diff --git a/browser/base/content/test/general/browser_URLBarSetURI.js b/browser/base/content/test/general/browser_URLBarSetURI.js
index 4df1c0af89f..5b2a4cf7d93 100644
--- a/browser/base/content/test/general/browser_URLBarSetURI.js
+++ b/browser/base/content/test/general/browser_URLBarSetURI.js
@@ -70,12 +70,8 @@ function loadTabInWindow(win, callback) {
   info("Loading tab");
   let url = "http://user:pass@example.com/";
   let tab = win.gBrowser.selectedTab = win.gBrowser.addTab(url);
-  tab.linkedBrowser.addEventListener("load", function listener() {
+  BrowserTestUtils.browserLoaded(tab.linkedBrowser, false, url).then(() => {
     info("Tab loaded");
-    if (tab.linkedBrowser.currentURI.spec != url)
-      return;
-    tab.linkedBrowser.removeEventListener("load", listener, true);
-
     is(win.gURLBar.textValue, "example.com", "URL bar had user/pass stripped initially");
     callback(tab);
   }, true);
diff --git a/browser/base/content/test/general/browser_bug329212.js b/browser/base/content/test/general/browser_bug329212.js
index 16c2bf4f6ad..b7b5165efae 100644
--- a/browser/base/content/test/general/browser_bug329212.js
+++ b/browser/base/content/test/general/browser_bug329212.js
@@ -2,9 +2,7 @@ function test () {
 
   waitForExplicitFinish();
   gBrowser.selectedTab = gBrowser.addTab();
-  gBrowser.selectedBrowser.addEventListener("load", function () {
-    gBrowser.selectedBrowser.removeEventListener("load", arguments.callee, true);
-
+  BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser).then(() => {
     let doc = gBrowser.contentDocument;
     let tooltip = document.getElementById("aHTMLTooltip");
 
@@ -35,9 +33,10 @@ function test () {
 
     gBrowser.removeCurrentTab();
     finish();
-  }, true);
+  });
 
-  content.location = 
-    "http://mochi.test:8888/browser/browser/base/content/test/general/title_test.svg";
+  gBrowser.loadURI(
+    "http://mochi.test:8888/browser/browser/base/content/test/general/title_test.svg"
+  );
 }
 
diff --git a/browser/base/content/test/general/browser_bug331772_xul_tooltiptext_in_html.js b/browser/base/content/test/general/browser_bug331772_xul_tooltiptext_in_html.js
index c88f049af3c..c9176d2c0a3 100644
--- a/browser/base/content/test/general/browser_bug331772_xul_tooltiptext_in_html.js
+++ b/browser/base/content/test/general/browser_bug331772_xul_tooltiptext_in_html.js
@@ -4,9 +4,7 @@
 function test () {
   waitForExplicitFinish();
   gBrowser.selectedTab = gBrowser.addTab();
-  gBrowser.selectedBrowser.addEventListener("load", function () {
-    gBrowser.selectedBrowser.removeEventListener("load", arguments.callee, true);
-
+  BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser).then(() => {
     let doc = gBrowser.contentDocument;
     let tooltip = document.getElementById("aHTMLTooltip");
 
@@ -15,9 +13,10 @@ function test () {
 
     gBrowser.removeCurrentTab();
     finish();
-  }, true);
+  });
 
-  content.location = 
-    "http://mochi.test:8888/browser/browser/base/content/test/general/xul_tooltiptext.xhtml";
+  gBrowser.loadURI(
+    "http://mochi.test:8888/browser/browser/base/content/test/general/xul_tooltiptext.xhtml"
+  );
 }
 
diff --git a/browser/base/content/test/general/browser_bug431826.js b/browser/base/content/test/general/browser_bug431826.js
index be655a3e5d7..b19ac5fe918 100644
--- a/browser/base/content/test/general/browser_bug431826.js
+++ b/browser/base/content/test/general/browser_bug431826.js
@@ -1,42 +1,63 @@
-function test() {
-  waitForExplicitFinish();
-
-  gBrowser.selectedTab = gBrowser.addTab();
-
-  // Navigate to a site with a broken cert
-  window.addEventListener("DOMContentLoaded", testBrokenCert, true);
-  content.location = "https://nocert.example.com/";
+function remote(task) {
+  return ContentTask.spawn(gBrowser.selectedBrowser, null, task);
 }
 
-function testBrokenCert() {
-  if (gBrowser.contentDocument.documentURI === "about:blank")
-    return;
-  window.removeEventListener("DOMContentLoaded", testBrokenCert, true);
+add_task(function* () {
+  gBrowser.selectedTab = gBrowser.addTab();
+
+  let promise = remote(function () {
+    return ContentTaskUtils.waitForEvent(this, "DOMContentLoaded", true, event => {
+      return content.document.documentURI != "about:blank";
+    }).then(() => 0); // don't want to send the event to the chrome process
+  });
+  gBrowser.loadURI("https://nocert.example.com/");
+  yield promise;
+
+  let uri = yield remote(() => {
+    return content.document.documentURI;
+  });
 
   // Confirm that we are displaying the contributed error page, not the default
-  ok(gBrowser.contentDocument.documentURI.startsWith("about:certerror"), "Broken page should go to about:certerror, not about:neterror");
+  ok(uri.startsWith("about:certerror"), "Broken page should go to about:certerror, not about:neterror");
+
+  let advancedDiv, advancedDivVisibility, technicalDivCollapsed;
+
+  [advancedDiv, advancedDivVisibility] = yield remote(() => {
+    let div = content.document.getElementById("advancedPanel");
+    if (div) {
+      return [true, div.ownerDocument.defaultView.getComputedStyle(div, "").visibility];
+    } else {
+      return [null, null];
+    }
+  });
 
   // Confirm that the expert section is collapsed
-  var advancedDiv = gBrowser.contentDocument.getElementById("advancedPanel");
   ok(advancedDiv, "Advanced content div should exist");
-  is_element_hidden(advancedDiv, "Advanced content should not be visible by default");
+  is(advancedDivVisibility, "hidden", "Advanced content should not be visible by default");
 
   // Tweak the expert mode pref
   gPrefService.setBoolPref("browser.xul.error_pages.expert_bad_cert", true);
 
-  window.addEventListener("DOMContentLoaded", testExpertPref, true);
+  promise = remote(function () {
+    return ContentTaskUtils.waitForEvent(this, "DOMContentLoaded", true);
+  });
   gBrowser.reload();
-}
+  yield promise;
+
+  [advancedDiv, advancedDivVisibility] = yield remote(() => {
+    let div = content.document.getElementById("advancedPanel");
+    if (div) {
+      return [true, div.ownerDocument.defaultView.getComputedStyle(div, "").visibility];
+    } else {
+      return [null, null];
+    }
+  });
 
-function testExpertPref() {
-  window.removeEventListener("DOMContentLoaded", testExpertPref, true);
-  var advancedDiv = gBrowser.contentDocument.getElementById("advancedPanel");
   ok(advancedDiv, "Advanced content div should exist");
-  is_element_visible(advancedDiv, "Advanced content should be visible by default");
+  is(advancedDivVisibility, "visible", "Advanced content should be visible by default");
 
   // Clean up
   gBrowser.removeCurrentTab();
   if (gPrefService.prefHasUserValue("browser.xul.error_pages.expert_bad_cert"))
     gPrefService.clearUserPref("browser.xul.error_pages.expert_bad_cert");
-  finish();
-}
+});
diff --git a/browser/base/content/test/general/browser_bug435035.js b/browser/base/content/test/general/browser_bug435035.js
index 07add048e4a..7570ef0d7e3 100644
--- a/browser/base/content/test/general/browser_bug435035.js
+++ b/browser/base/content/test/general/browser_bug435035.js
@@ -2,15 +2,16 @@ function test() {
   waitForExplicitFinish();
 
   gBrowser.selectedTab = gBrowser.addTab();
-  gBrowser.selectedBrowser.addEventListener("load", function () {
-    gBrowser.selectedBrowser.removeEventListener("load", arguments.callee, true);
+  BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser).then(() => {
     is(document.getElementById("identity-box").className,
        "unknownIdentity mixedDisplayContent",
        "identity box has class name for mixed content");
 
     gBrowser.removeCurrentTab();
     finish();
-  }, true);
+  });
 
-  content.location = "https://example.com/browser/browser/base/content/test/general/test_bug435035.html";
+  gBrowser.loadURI(
+    "https://example.com/browser/browser/base/content/test/general/test_bug435035.html"
+  );
 }
diff --git a/browser/base/content/test/general/browser_bug441778.js b/browser/base/content/test/general/browser_bug441778.js
index ef68018a0d1..133e06d0ed7 100644
--- a/browser/base/content/test/general/browser_bug441778.js
+++ b/browser/base/content/test/general/browser_bug441778.js
@@ -30,16 +30,16 @@ function test() {
     // Start the sub-document load.
     let deferred = Promise.defer();
     executeSoon(function () {
-      testBrowser.addEventListener("load", function (e) {
-        testBrowser.removeEventListener("load", arguments.callee, true);
-
-        is(e.target.defaultView.location, TEST_IFRAME_URL, "got the load event for the iframe");
+      BrowserTestUtils.browserLoaded(testBrowser, true).then(url => {
+        is(url, TEST_IFRAME_URL, "got the load event for the iframe");
         is(ZoomManager.zoom, zoomLevel, "zoom is retained after sub-document load");
 
         FullZoomHelper.removeTabAndWaitForLocationChange().
           then(() => deferred.resolve());
-      }, true);
-      content.document.querySelector("iframe").src = TEST_IFRAME_URL;
+      });
+      ContentTask.spawn(testBrowser, TEST_IFRAME_URL, url => {
+        content.document.querySelector("iframe").src = url;
+      });
     });
     yield deferred.promise;
   }).then(finish, FullZoomHelper.failAndContinue(finish));
diff --git a/browser/base/content/test/general/browser_bug553455.js b/browser/base/content/test/general/browser_bug553455.js
index 19669b00d09..182be79b911 100644
--- a/browser/base/content/test/general/browser_bug553455.js
+++ b/browser/base/content/test/general/browser_bug553455.js
@@ -803,12 +803,9 @@ function test_urlbar() {
 
 function test_wronghost() {
   gBrowser.selectedTab = gBrowser.addTab();
-  gBrowser.addEventListener("load", function() {
-    if (gBrowser.currentURI.spec != TESTROOT2 + "enabled.html")
-      return;
-
-    gBrowser.removeEventListener("load", arguments.callee, true);
 
+  let requestedUrl = TESTROOT2 + "enabled.html";
+  BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser, false, requestedUrl).then(() => {
     // Wait for the progress notification
     wait_for_progress_notification(function(aPanel) {
       // Wait for the complete notification
@@ -825,7 +822,7 @@ function test_wronghost() {
     });
 
     gBrowser.loadURI(TESTROOT + "corrupt.xpi");
-  }, true);
+  });
   gBrowser.loadURI(TESTROOT2 + "enabled.html");
 },
 
@@ -848,12 +845,8 @@ function test_reload() {
 
         PopupNotifications.panel.addEventListener("popuphiding", test_fail, false);
 
-        gBrowser.addEventListener("load", function() {
-          if (gBrowser.currentURI.spec != TESTROOT2 + "enabled.html")
-            return;
-
-          gBrowser.removeEventListener("load", arguments.callee, true);
-
+        let requestedUrl = TESTROOT2 + "enabled.html";
+        BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser, false, requestedUrl).then(() => {
           PopupNotifications.panel.removeEventListener("popuphiding", test_fail, false);
 
           AddonManager.getAllInstalls(function(aInstalls) {
@@ -864,7 +857,7 @@ function test_reload() {
             wait_for_notification_close(runNextTest);
             gBrowser.removeTab(gBrowser.selectedTab);
           });
-        }, true);
+        });
         gBrowser.loadURI(TESTROOT2 + "enabled.html");
       });
 
diff --git a/browser/base/content/test/general/browser_bug561623.js b/browser/base/content/test/general/browser_bug561623.js
index 6f7fc85c77c..5d75f8b7804 100644
--- a/browser/base/content/test/general/browser_bug561623.js
+++ b/browser/base/content/test/general/browser_bug561623.js
@@ -1,9 +1,7 @@
 function test() {
   waitForExplicitFinish();
   gBrowser.selectedTab = gBrowser.addTab();
-  gBrowser.selectedBrowser.addEventListener("load", function () {
-    gBrowser.selectedBrowser.removeEventListener("load", arguments.callee, true);
-
+  BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser).then(() => {
     let doc = gBrowser.contentDocument;
     let tooltip = document.getElementById("aHTMLTooltip");
     let i = doc.getElementById("i");
@@ -21,9 +19,10 @@ function test() {
 
     gBrowser.removeCurrentTab();
     finish();
-  }, true);
+  });
 
-  content.location = 
-    "data:text/html,<!DOCTYPE html><html><body><input id='i'></body></html>";
+  gBrowser.loadURI(
+    "data:text/html,<!DOCTYPE html><html><body><input id='i'></body></html>"
+  );
 }
 
diff --git a/browser/base/content/test/general/browser_bug562649.js b/browser/base/content/test/general/browser_bug562649.js
index ad37a40c5df..32870133d92 100644
--- a/browser/base/content/test/general/browser_bug562649.js
+++ b/browser/base/content/test/general/browser_bug562649.js
@@ -14,13 +14,11 @@ function test() {
   is(gURLBar.value, URI, "location bar value matches test URI after switching tabs");
 
   waitForExplicitFinish();
-  gBrowser.selectedBrowser.addEventListener("load", function () {
-    gBrowser.selectedBrowser.removeEventListener("load", arguments.callee, true);
-
+  BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser).then(() => {
     is(gBrowser.userTypedValue, null, "userTypedValue is null as the page has loaded");
     is(gURLBar.value, URI, "location bar value matches test URI as the page has loaded");
 
     gBrowser.removeCurrentTab();
     finish();
-  }, true);
+  });
 }
diff --git a/browser/base/content/test/general/browser_bug578534.js b/browser/base/content/test/general/browser_bug578534.js
index 5cf83cc6683..e8d1f60eb5a 100644
--- a/browser/base/content/test/general/browser_bug578534.js
+++ b/browser/base/content/test/general/browser_bug578534.js
@@ -8,19 +8,18 @@ function test() {
   let uriObj = Services.io.newURI(uriString, null, null)
   let cp = Components.classes["@mozilla.org/cookie/permission;1"]
                      .getService(Components.interfaces.nsICookiePermission);
-  
+
   Services.prefs.setIntPref(cookieBehavior, 2);
 
   cp.setAccess(uriObj, cp.ACCESS_ALLOW);
   gBrowser.selectedTab = gBrowser.addTab(uriString);
   waitForExplicitFinish();
-  gBrowser.selectedBrowser.addEventListener("load", onTabLoaded, true);
-  
+  BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser).then(onTabLoaded);
+
   function onTabLoaded() {
     is(gBrowser.selectedBrowser.contentWindow.navigator.cookieEnabled, true,
        "navigator.cookieEnabled should be true");
     // Clean up
-    gBrowser.selectedBrowser.removeEventListener("load", onTabLoaded, true);
     gBrowser.removeTab(gBrowser.selectedTab);
     Services.prefs.setIntPref(cookieBehavior, 0);
     cp.setAccess(uriObj, cp.ACCESS_DEFAULT);
diff --git a/browser/base/content/test/general/browser_bug579872.js b/browser/base/content/test/general/browser_bug579872.js
index 63f64598da9..f449c16ddb4 100644
--- a/browser/base/content/test/general/browser_bug579872.js
+++ b/browser/base/content/test/general/browser_bug579872.js
@@ -5,8 +5,8 @@
 function test() {
   let newTab = gBrowser.addTab();
   waitForExplicitFinish();
-  newTab.linkedBrowser.addEventListener("load", mainPart, true);
-  
+  BrowserTestUtils.browserLoaded(newTab.linkedBrowser).then(mainPart);
+
   function mainPart() {
     gBrowser.pinTab(newTab);
     gBrowser.selectedTab = newTab;
@@ -20,7 +20,6 @@ function test() {
     openUILinkIn("http://example.org/", "current");
     is(gBrowser.tabs.length, 3, "Should open in new tab");
     
-    newTab.removeEventListener("load", mainPart, true);
     gBrowser.removeTab(newTab);
     gBrowser.removeTab(gBrowser.tabs[1]); // example.org tab
     finish();
diff --git a/browser/base/content/test/general/browser_bug580956.js b/browser/base/content/test/general/browser_bug580956.js
index bcbfdceb7e4..b8e7bc20b7e 100644
--- a/browser/base/content/test/general/browser_bug580956.js
+++ b/browser/base/content/test/general/browser_bug580956.js
@@ -17,12 +17,10 @@ function test() {
 
   var tab = gBrowser.addTab("http://mochi.test:8888/");
   var browser = gBrowser.getBrowserForTab(tab);
-  browser.addEventListener("load", function() {
-    browser.removeEventListener("load", arguments.callee, true);
-
+  BrowserTestUtils.browserLoaded(browser).then(() => {
     BrowserTestUtils.removeTab(tab).then(() => {
       ok(isUndoCloseEnabled(), "Undo Close Tab should be enabled.");
       finish();
     });
-  }, true);
+  });
 }
diff --git a/browser/base/content/test/general/browser_bug581947.js b/browser/base/content/test/general/browser_bug581947.js
index 48bffaea109..5beda3a4d49 100644
--- a/browser/base/content/test/general/browser_bug581947.js
+++ b/browser/base/content/test/general/browser_bug581947.js
@@ -58,9 +58,7 @@ function todo_check(aElementName, aBarred) {
 function test () {
   waitForExplicitFinish();
   gBrowser.selectedTab = gBrowser.addTab();
-  gBrowser.selectedBrowser.addEventListener("load", function () {
-    gBrowser.selectedBrowser.removeEventListener("load", arguments.callee, true);
-
+  BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser).then(() => {
     let testData = [
     /* element name, barred */
       [ 'input',    false,  null],
@@ -87,9 +85,10 @@ function test () {
 
     gBrowser.removeCurrentTab();
     finish();
-  }, true);
+  });
 
-  content.location = 
-    "data:text/html,<!DOCTYPE html><html><body><form id='content'></form></body></html>";
+  gBrowser.loadURI(
+    "data:text/html,<!DOCTYPE html><html><body><form id='content'></form></body></html>"
+  );
 }
 
diff --git a/browser/base/content/test/general/browser_bug594131.js b/browser/base/content/test/general/browser_bug594131.js
index d68d1979af2..ce09026ace4 100644
--- a/browser/base/content/test/general/browser_bug594131.js
+++ b/browser/base/content/test/general/browser_bug594131.js
@@ -5,11 +5,9 @@
 function test() {
   let newTab = gBrowser.addTab("http://example.com");
   waitForExplicitFinish();
-  newTab.linkedBrowser.addEventListener("load", mainPart, true);
+  BrowserTestUtils.browserLoaded(newTab.linkedBrowser).then(mainPart);
 
   function mainPart() {
-    newTab.linkedBrowser.removeEventListener("load", mainPart, true);
-
     gBrowser.pinTab(newTab);
     gBrowser.selectedTab = newTab;
 
diff --git a/browser/base/content/test/general/browser_bug624734.js b/browser/base/content/test/general/browser_bug624734.js
index fd9c6766355..d6fc7acbcf3 100644
--- a/browser/base/content/test/general/browser_bug624734.js
+++ b/browser/base/content/test/general/browser_bug624734.js
@@ -17,15 +17,13 @@ function test() {
   waitForExplicitFinish();
 
   let tab = gBrowser.selectedTab = gBrowser.addTab();
-  tab.linkedBrowser.addEventListener("load", (function(event) {
-    tab.linkedBrowser.removeEventListener("load", arguments.callee, true);
-
+  BrowserTestUtils.browserLoaded(tab.linkedBrowser).then(() => {
     if (BookmarkingUI.status == BookmarkingUI.STATUS_UPDATING) {
       waitForCondition(() => BookmarkingUI.status != BookmarkingUI.STATUS_UPDATING, finishTest, "BookmarkingUI was updating for too long");
     } else {
       finishTest();
     }
-  }), true);
+  });
 
   tab.linkedBrowser.loadURI("http://example.com/browser/browser/base/content/test/general/dummy_page.html");
 }
diff --git a/browser/base/content/test/general/browser_bug633691.js b/browser/base/content/test/general/browser_bug633691.js
index 58eff1da038..b2e3a22ba2d 100644
--- a/browser/base/content/test/general/browser_bug633691.js
+++ b/browser/base/content/test/general/browser_bug633691.js
@@ -4,17 +4,12 @@
 
 function test() {
   waitForExplicitFinish();
-  gBrowser.selectedTab = gBrowser.addTab();
+  gBrowser.selectedTab = gBrowser.addTab("data:text/html,<iframe width='700' height='700' src='about:certerror'></iframe>");
   // Open a html page with about:certerror in an iframe
-  gBrowser.selectedBrowser.addEventListener("load", testIframeCert, true);
-  content.location = "data:text/html,<iframe width='700' height='700' src='about:certerror'></iframe>";
+  BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser).then(testIframeCert);
 }
 
 function testIframeCert(e) {
-  if (e.target.location.href == "about:blank") {
-    return;
-  }
-  gBrowser.selectedBrowser.removeEventListener("load", testIframeCert, true);
   // Confirm that the expert section is hidden
   var doc = gBrowser.contentDocument.getElementsByTagName('iframe')[0].contentDocument;
   var aP = doc.getElementById("advancedPanel");
diff --git a/browser/base/content/test/general/browser_bug676619.js b/browser/base/content/test/general/browser_bug676619.js
index 03211f9698a..1afc48faac5 100644
--- a/browser/base/content/test/general/browser_bug676619.js
+++ b/browser/base/content/test/general/browser_bug676619.js
@@ -3,14 +3,7 @@ function test () {
 
   var isHTTPS = false;
 
-  gBrowser.selectedTab = gBrowser.addTab();
-  gBrowser.selectedBrowser.addEventListener("load", function () {
-    if (isHTTPS) {
-      gBrowser.selectedBrowser.removeEventListener("load", arguments.callee, true);
-    }
-    let doc = gBrowser.contentDocument;
-
-
+  function loadListener() {
     function testLocation(link, url, next) {
       var tabOpenListener = new TabOpenListener(url, function () {
           gBrowser.removeTab(this.tab);
@@ -18,18 +11,26 @@ function test () {
         next();
       });
 
-      doc.getElementById(link).click();
+      ContentTask.spawn(gBrowser.selectedBrowser, link, link => {
+        content.document.getElementById(link).click();
+      });
     }
 
     function testLink(link, name, next) {
-        addWindowListener("chrome://mozapps/content/downloads/unknownContentType.xul", function (win) {
-            is(doc.getElementById("unload-flag").textContent, "Okay", "beforeunload shouldn't have fired");
-            is(win.document.getElementById("location").value, name, "file name should match");
-            win.close();
-            next();
+      addWindowListener("chrome://mozapps/content/downloads/unknownContentType.xul", function (win) {
+        ContentTask.spawn(gBrowser.selectedBrowser, null, () => {
+          return content.document.getElementById("unload-flag").textContent;
+        }).then(unloadFlag => {
+          is(unloadFlag, "Okay", "beforeunload shouldn't have fired");
+          is(win.document.getElementById("location").value, name, "file name should match");
+          win.close();
+          next();
         });
+      });
 
-        doc.getElementById(link).click();
+      ContentTask.spawn(gBrowser.selectedBrowser, link, link => {
+        content.document.getElementById(link).click();
+      });
     }
 
     testLink("link1", "test.txt",
@@ -41,18 +42,22 @@ function test () {
                 testLocation.bind(null, "link7", "http://example.com/",
                   function () {
                     if (isHTTPS) {
-                      gBrowser.removeCurrentTab();
                       finish();
                     } else {
                       // same test again with https:
                       isHTTPS = true;
-                      content.location = "https://example.com:443/browser/browser/base/content/test/general/download_page.html";
+                      gBrowser.loadURI("https://example.com:443/browser/browser/base/content/test/general/download_page.html");
                     }
                   })))))));
 
-  }, true);
+  }
 
-  content.location = "http://mochi.test:8888/browser/browser/base/content/test/general/download_page.html";
+  BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser).then(() => {
+    loadListener();
+    BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser).then(loadListener);
+  });
+
+  gBrowser.loadURI("http://mochi.test:8888/browser/browser/base/content/test/general/download_page.html");
 }
 
 
@@ -97,15 +102,12 @@ TabOpenListener.prototype = {
       gBrowser.tabContainer.removeEventListener("TabOpen", this, false);
       this.tab = event.originalTarget;
       this.browser = this.tab.linkedBrowser;
-      gBrowser.addEventListener("pageshow", this, false);
-    } else if (event.type == "pageshow") {
-      if (event.target.location.href != this.url)
-        return;
-      gBrowser.removeEventListener("pageshow", this, false);
-      this.tab.addEventListener("TabClose", this, false);
-      var url = this.browser.contentDocument.location.href;
-      is(url, this.url, "Should have opened the correct tab");
-      this.opencallback(this.tab, this.browser.contentWindow);
+      BrowserTestUtils.browserLoaded(this.browser, false, this.url).then(() => {
+        this.tab.addEventListener("TabClose", this, false);
+        var url = this.browser.currentURI.spec;
+        is(url, this.url, "Should have opened the correct tab");
+        this.opencallback();
+      });
     } else if (event.type == "TabClose") {
       if (event.originalTarget != this.tab)
         return;
diff --git a/browser/base/content/test/general/browser_bug902156.js b/browser/base/content/test/general/browser_bug902156.js
index 51fe6450576..97e333fb4b6 100644
--- a/browser/base/content/test/general/browser_bug902156.js
+++ b/browser/base/content/test/general/browser_bug902156.js
@@ -45,10 +45,7 @@ function cleanUpAfterTests() {
 //------------------------ Test 1 ------------------------------
 
 function test1A() {
-  // Removing EventListener because we have to register a new
-  // one once the page is loaded with mixed content blocker disabled
-  gTestBrowser.removeEventListener("load", test1A, true);
-  gTestBrowser.addEventListener("load", test1B, true);
+  BrowserTestUtils.browserLoaded(gTestBrowser).then(test1B);
 
   assertMixedContentBlockingState(gTestBrowser, {activeLoaded: false, activeBlocked: true, passiveLoaded: false});
 
@@ -65,21 +62,18 @@ function test1B() {
 }
 
 function test1C() {
-  gTestBrowser.removeEventListener("load", test1B, true);
   var actual = content.document.getElementById('mctestdiv').innerHTML;
   is(actual, "Mixed Content Blocker disabled", "OK: Executed mixed script in Test 1C");
 
   // The Script loaded after we disabled the page, now we are going to reload the
   // page and see if our decision is persistent
-  gTestBrowser.addEventListener("load", test1D, true);
+  BrowserTestUtils.browserLoaded(gTestBrowser).then(test1D);
 
   var url = gHttpTestRoot1 + "file_bug902156_2.html";
-  gTestBrowser.contentWindow.location = url;
+  gTestBrowser.loadURI(url);
 }
 
 function test1D() {
-  gTestBrowser.removeEventListener("load", test1D, true);
-
   // The Control Center button should appear but isMixedContentBlocked should be NOT true,
   // because our decision of disabling the mixed content blocker is persistent.
   assertMixedContentBlockingState(gTestBrowser, {activeLoaded: true, activeBlocked: false, passiveLoaded: false});
@@ -94,16 +88,13 @@ function test1D() {
 //------------------------ Test 2 ------------------------------
 
 function test2() {
-  gTestBrowser.addEventListener("load", test2A, true);
+  BrowserTestUtils.browserLoaded(gTestBrowser).then(test2A);
   var url = gHttpTestRoot2 + "file_bug902156_2.html";
-  gTestBrowser.contentWindow.location = url;
+  gTestBrowser.loadURI(url);
 }
 
 function test2A() {
-  // Removing EventListener because we have to register a new
-  // one once the page is loaded with mixed content blocker disabled
-  gTestBrowser.removeEventListener("load", test2A, true);
-  gTestBrowser.addEventListener("load", test2B, true);
+  BrowserTestUtils.browserLoaded(gTestBrowser).then(test2B);
 
   assertMixedContentBlockingState(gTestBrowser, {activeLoaded: false, activeBlocked: true, passiveLoaded: false});
 
@@ -120,13 +111,12 @@ function test2B() {
 }
 
 function test2C() {
-  gTestBrowser.removeEventListener("load", test2B, true);
   var actual = content.document.getElementById('mctestdiv').innerHTML;
   is(actual, "Mixed Content Blocker disabled", "OK: Executed mixed script in Test 2C");
 
   // The Script loaded after we disabled the page, now we are going to reload the
   // page and see if our decision is persistent
-  gTestBrowser.addEventListener("load", test2D, true);
+  BrowserTestUtils.browserLoaded(gTestBrowser).then(test2D);
 
   // reload the page using the provided link in the html file
   var mctestlink = content.document.getElementById("mctestlink");
@@ -134,8 +124,6 @@ function test2C() {
 }
 
 function test2D() {
-  gTestBrowser.removeEventListener("load", test2D, true);
-
   // The Control Center button should appear but isMixedContentBlocked should be NOT true,
   // because our decision of disabling the mixed content blocker is persistent.
   assertMixedContentBlockingState(gTestBrowser, {activeLoaded: true, activeBlocked: false, passiveLoaded: false});
@@ -150,16 +138,12 @@ function test2D() {
 //------------------------ Test 3 ------------------------------
 
 function test3() {
-  gTestBrowser.addEventListener("load", test3A, true);
+  BrowserTestUtils.browserLoaded(gTestBrowser).then(test3A);
   var url = gHttpTestRoot1 + "file_bug902156_3.html";
-  gTestBrowser.contentWindow.location = url;
+  gTestBrowser.loadURI(url);
 }
 
 function test3A() {
-  // Removing EventListener because we have to register a new
-  // one once the page is loaded with mixed content blocker disabled
-  gTestBrowser.removeEventListener("load", test3A, true);
-
   assertMixedContentBlockingState(gTestBrowser, {activeLoaded: false, activeBlocked: true, passiveLoaded: false});
 
   // We are done with tests, clean up
@@ -184,7 +168,7 @@ function test() {
   newTab.linkedBrowser.stop()
 
   // Starting Test Number 1:
-  gTestBrowser.addEventListener("load", test1A, true);
+  BrowserTestUtils.browserLoaded(gTestBrowser).then(test1A);
   var url = gHttpTestRoot1 + "file_bug902156_1.html";
-  gTestBrowser.contentWindow.location = url;
+  gTestBrowser.loadURI(url);
 }
diff --git a/browser/base/content/test/general/browser_findbarClose.js b/browser/base/content/test/general/browser_findbarClose.js
index 9b61ff9e971..5f8d36f9bdb 100644
--- a/browser/base/content/test/general/browser_findbarClose.js
+++ b/browser/base/content/test/general/browser_findbarClose.js
@@ -3,32 +3,27 @@
 
 // Tests find bar auto-close behavior
 
-var newTab, iframe;
+var newTab;
 
-function test() {
+add_task(function* findbar_test() {
   waitForExplicitFinish();
   newTab = gBrowser.addTab("about:blank");
-  newTab.linkedBrowser.addEventListener("DOMContentLoaded",
-    prepareTestFindBarStaysOpenOnSubdocumentLocationChange, false);
-  newTab.linkedBrowser.contentWindow.location = "http://example.com/browser/" +
-    "browser/base/content/test/general/test_bug628179.html";
-}
 
-function prepareTestFindBarStaysOpenOnSubdocumentLocationChange() {
-  newTab.linkedBrowser.removeEventListener("DOMContentLoaded",
-    prepareTestFindBarStaysOpenOnSubdocumentLocationChange, false);
+  let promise = ContentTask.spawn(newTab.linkedBrowser, null, function* () {
+    yield ContentTaskUtils.waitForEvent(this, "DOMContentLoaded", false);
+  });
+  newTab.linkedBrowser.loadURI("http://example.com/browser/" +
+    "browser/base/content/test/general/test_bug628179.html");
+  yield promise;
 
   gFindBar.open();
 
-  iframe = newTab.linkedBrowser.contentDocument.getElementById("iframe");
-  iframe.addEventListener("load",
-    testFindBarStaysOpenOnSubdocumentLocationChange, false);
-  iframe.src = "http://example.org/";
-}
-
-function testFindBarStaysOpenOnSubdocumentLocationChange() {
-  iframe.removeEventListener("load",
-    testFindBarStaysOpenOnSubdocumentLocationChange, false);
+  yield new ContentTask.spawn(newTab.linkedBrowser, null, function* () {
+    let iframe = content.document.getElementById("iframe");
+    let promise = ContentTaskUtils.waitForEvent(iframe, "load", false);
+    iframe.src = "http://example.org/";
+    yield promise;
+  });
 
   ok(!gFindBar.hidden, "the Find bar isn't hidden after the location of a " +
      "subdocument changes");
@@ -36,5 +31,5 @@ function testFindBarStaysOpenOnSubdocumentLocationChange() {
   gFindBar.close();
   gBrowser.removeTab(newTab);
   finish();
-}
+});
 
diff --git a/browser/base/content/test/general/browser_popupUI.js b/browser/base/content/test/general/browser_popupUI.js
index fd722886d00..55c9d45fec4 100644
--- a/browser/base/content/test/general/browser_popupUI.js
+++ b/browser/base/content/test/general/browser_popupUI.js
@@ -3,17 +3,16 @@ function test() {
   gPrefService.setBoolPref("dom.disable_open_during_load", false);
 
   var browser = gBrowser.selectedBrowser;
-  browser.addEventListener("load", function () {
-    browser.removeEventListener("load", arguments.callee, true);
-
+  BrowserTestUtils.browserLoaded(browser).then(() => {
     if (gPrefService.prefHasUserValue("dom.disable_open_during_load"))
       gPrefService.clearUserPref("dom.disable_open_during_load");
 
     findPopup();
-  }, true);
+  });
 
-  content.location =
-    "data:text/html,<html><script>popup=open('about:blank','','width=300,height=200')</script>";
+  browser.loadURI(
+    "data:text/html,<html><script>popup=open('about:blank','','width=300,height=200')</script>"
+  );
 }
 
 function findPopup() {
diff --git a/browser/base/content/test/general/browser_utilityOverlay.js b/browser/base/content/test/general/browser_utilityOverlay.js
index a3d909eb774..04e0c85a615 100644
--- a/browser/base/content/test/general/browser_utilityOverlay.js
+++ b/browser/base/content/test/general/browser_utilityOverlay.js
@@ -41,22 +41,20 @@ function test_getBoolPref() {
 function test_openNewTabWith() {
   openNewTabWith("http://example.com/");
   let tab = gBrowser.selectedTab = gBrowser.tabs[1];
-  tab.linkedBrowser.addEventListener("load", function onLoad(event) {
-    tab.linkedBrowser.removeEventListener("load", onLoad, true);
+  BrowserTestUtils.browserLoaded(tab.linkedBrowser).then(() => {
     is(tab.linkedBrowser.currentURI.spec, "http://example.com/", "example.com loaded");
     gBrowser.removeCurrentTab();
     runNextTest();
-  }, true);
+  });
 }
 
 function test_openUILink() {
   let tab = gBrowser.selectedTab = gBrowser.addTab("about:blank");
-  tab.linkedBrowser.addEventListener("load", function onLoad(event) {
-    tab.linkedBrowser.removeEventListener("load", onLoad, true);
+  BrowserTestUtils.browserLoaded(tab.linkedBrowser).then(() => {
     is(tab.linkedBrowser.currentURI.spec, "http://example.org/", "example.org loaded");
     gBrowser.removeCurrentTab();
     runNextTest();
-  }, true);
+  });
 
   openUILink("http://example.org/"); // defaults to "current"
 }
diff --git a/browser/components/sessionstore/test/browser_522545.js b/browser/components/sessionstore/test/browser_522545.js
index a002b2b921d..73395d579db 100644
--- a/browser/components/sessionstore/test/browser_522545.js
+++ b/browser/components/sessionstore/test/browser_522545.js
@@ -6,7 +6,7 @@ function test() {
   /** Test for Bug 522545 **/
 
   waitForExplicitFinish();
-  requestLongerTimeout(2);
+  requestLongerTimeout(3);
 
   // This tests the following use case:
   // User opens a new tab which gets focus. The user types something into the
@@ -159,12 +159,10 @@ function test() {
 
       ok(hasUTV, "At least one tab has a userTypedValue with userTypedClear with no loaded URL");
 
-      gBrowser.addEventListener("load", firstLoad, true);
+      BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser).then(firstLoad);
     }
 
     function firstLoad() {
-      gBrowser.removeEventListener("load", firstLoad, true);
-
       let state = JSON.parse(ss.getBrowserState());
       let hasSH = state.windows[0].tabs.some(function(aTab) {
         return !("userTypedValue" in aTab) && aTab.entries[0].url;
diff --git a/devtools/client/framework/test/browser_target_events.js b/devtools/client/framework/test/browser_target_events.js
index 9b95f011a5c..2eb8a4038f0 100644
--- a/devtools/client/framework/test/browser_target_events.js
+++ b/devtools/client/framework/test/browser_target_events.js
@@ -9,12 +9,10 @@ function test()
   waitForExplicitFinish();
 
   gBrowser.selectedTab = gBrowser.addTab();
-  gBrowser.selectedBrowser.addEventListener("load", onLoad, true);
+  BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser).then(onLoad);
 }
 
-function onLoad(evt) {
-  gBrowser.selectedBrowser.removeEventListener(evt.type, onLoad, true);
-
+function onLoad() {
   target = TargetFactory.forTab(gBrowser.selectedTab);
 
   is(target.tab, gBrowser.selectedTab, "Target linked to the right tab.");
diff --git a/devtools/client/shared/test/browser_mdn-docs-01.js b/devtools/client/shared/test/browser_mdn-docs-01.js
index e0930150fcf..7e426ec5545 100644
--- a/devtools/client/shared/test/browser_mdn-docs-01.js
+++ b/devtools/client/shared/test/browser_mdn-docs-01.js
@@ -131,26 +131,22 @@ function* testTheBasics(widget) {
   */
 function checkLinkClick(link) {
 
-  function loadListener(e) {
-    let tab = e.target;
+  function loadListener(tab) {
     var browser = getBrowser().getBrowserForTab(tab);
     var uri = browser.currentURI.spec;
-    // this is horrible, and it's because when we open a new tab
-    // "about:blank: is first loaded into it, before the actual
-    // document we want to load.
-    if (uri != "about:blank") {
-      info("New browser tab has loaded");
-      tab.removeEventListener("load", loadListener);
-      gBrowser.removeTab(tab);
-      info("Resolve promise with new tab URI");
-      deferred.resolve(uri);
-    }
+
+    info("New browser tab has loaded");
+    gBrowser.removeTab(tab);
+    info("Resolve promise with new tab URI");
+    deferred.resolve(uri);
   }
 
   function newTabListener(e) {
     gBrowser.tabContainer.removeEventListener("TabOpen", newTabListener);
     var tab = e.target;
-    tab.addEventListener("load", loadListener, false);
+    BrowserTestUtils.browserLoaded(tab.linkedBrowser, false,
+                                   url => { return url != "about:blank"; })
+      .then(url => loadListener(tab));
   }
 
   let deferred = promise.defer();
diff --git a/devtools/client/shared/test/head.js b/devtools/client/shared/test/head.js
index 5e41c4f00a2..340e4d2a762 100644
--- a/devtools/client/shared/test/head.js
+++ b/devtools/client/shared/test/head.js
@@ -27,17 +27,16 @@ function addTab(aURL, aCallback)
   waitForExplicitFinish();
 
   gBrowser.selectedTab = gBrowser.addTab();
-  content.location = aURL;
-
   let tab = gBrowser.selectedTab;
   let browser = gBrowser.getBrowserForTab(tab);
 
-  function onTabLoad() {
-    browser.removeEventListener("load", onTabLoad, true);
-    aCallback(browser, tab, browser.contentDocument);
-  }
+  let url = encodeURI(aURL);
 
-  browser.addEventListener("load", onTabLoad, true);
+  BrowserTestUtils.browserLoaded(browser, false, url).then(() => {
+    aCallback(browser, tab, browser.contentDocument);
+  });
+
+  browser.loadURI(url);
 }
 
 function promiseTab(aURL) {
diff --git a/devtools/client/sourceeditor/test/browser_css_getInfo.js b/devtools/client/sourceeditor/test/browser_css_getInfo.js
index 1dc1094d26b..de437860a47 100644
--- a/devtools/client/sourceeditor/test/browser_css_getInfo.js
+++ b/devtools/client/sourceeditor/test/browser_css_getInfo.js
@@ -123,12 +123,11 @@ var doc = null;
 function test() {
   waitForExplicitFinish();
   gBrowser.selectedTab = gBrowser.addTab();
-  gBrowser.selectedBrowser.addEventListener("load", function onload() {
-    gBrowser.selectedBrowser.removeEventListener("load", onload, true);
+  BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser).then(() => {
     doc = content.document;
     runTests();
-  }, true);
-  content.location = TEST_URI;
+  });
+  gBrowser.loadURI(TEST_URI);
 }
 
 function runTests() {
diff --git a/devtools/client/sourceeditor/test/browser_css_statemachine.js b/devtools/client/sourceeditor/test/browser_css_statemachine.js
index 1251e673dbe..6091113aa4c 100644
--- a/devtools/client/sourceeditor/test/browser_css_statemachine.js
+++ b/devtools/client/sourceeditor/test/browser_css_statemachine.js
@@ -58,13 +58,11 @@ const TEST_URI = "data:text/html;charset=UTF-8," + encodeURIComponent(
 var doc = null;
 function test() {
   waitForExplicitFinish();
-  gBrowser.selectedTab = gBrowser.addTab();
-  gBrowser.selectedBrowser.addEventListener("load", function onload() {
-    gBrowser.selectedBrowser.removeEventListener("load", onload, true);
+  gBrowser.selectedTab = gBrowser.addTab(TEST_URI);
+  BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser).then(() => {
     doc = content.document;
     runTests();
-  }, true);
-  content.location = TEST_URI;
+  });
 }
 
 function runTests() {
diff --git a/docshell/test/browser/browser_bug441169.js b/docshell/test/browser/browser_bug441169.js
index a7f2cb0c35f..01511579338 100644
--- a/docshell/test/browser/browser_bug441169.js
+++ b/docshell/test/browser/browser_bug441169.js
@@ -1,31 +1,37 @@
 /* Make sure that netError won't allow HTML injection through badcert parameters.  See bug 441169. */
 var newBrowser
 
-// An edited version of the standard neterror url which attempts to
-// insert a <span id="test_span"> tag into the text.  We will navigate to this page
-// and ensure that the span tag is not parsed as HTML.
-var chromeURL = "about:neterror?e=nssBadCert&u=https%3A//test.kuix.de/&c=UTF-8&d=This%20sentence%20should%20not%20be%20parsed%20to%20include%20a%20%3Cspan%20id=%22test_span%22%3Enamed%3C/span%3E%20span%20tag.%0A%0AThe%20certificate%20is%20only%20valid%20for%20%3Ca%20id=%22cert_domain_link%22%20title=%22kuix.de%22%3Ekuix.de%3C/a%3E%0A%0A(Error%20code%3A%20ssl_error_bad_cert_domain)";
+function task() {
+  let resolve;
+  let promise = new Promise(r => { resolve = r; });
+
+  addEventListener("DOMContentLoaded", checkPage, false);
+
+  function checkPage(event) {
+    if (event.target != content.document) {
+      return;
+    }
+    removeEventListener("DOMContentLoaded", checkPage, false);
+
+    is(content.document.getElementById("test_span"), null, "Error message should not be parsed as HTML, and hence shouldn't include the 'test_span' element.");
+    resolve();
+  }
+
+  var chromeURL = "about:neterror?e=nssBadCert&u=https%3A//test.kuix.de/&c=UTF-8&d=This%20sentence%20should%20not%20be%20parsed%20to%20include%20a%20%3Cspan%20id=%22test_span%22%3Enamed%3C/span%3E%20span%20tag.%0A%0AThe%20certificate%20is%20only%20valid%20for%20%3Ca%20id=%22cert_domain_link%22%20title=%22kuix.de%22%3Ekuix.de%3C/a%3E%0A%0A(Error%20code%3A%20ssl_error_bad_cert_domain)";
+  content.location = chromeURL;
+
+  return promise;
+}
 
 function test() {
   waitForExplicitFinish();
-  
+
   var newTab = gBrowser.addTab();
   gBrowser.selectedTab = newTab;
   newBrowser = gBrowser.getBrowserForTab(newTab);
-  
-  window.addEventListener("DOMContentLoaded", checkPage, false);
-  newBrowser.contentWindow.location = chromeURL;
-}
 
-function checkPage(event) {
-  if (event.target != gBrowser.selectedBrowser.contentDocument) {
-    return;
-  }
-
-  window.removeEventListener("DOMContentLoaded", checkPage, false);
-  
-  is(newBrowser.contentDocument.getElementById("test_span"), null, "Error message should not be parsed as HTML, and hence shouldn't include the 'test_span' element.");
-  
-  gBrowser.removeCurrentTab();
-  finish();
+  ContentTask.spawn(newBrowser, null, task).then(() => {
+    gBrowser.removeCurrentTab();
+    finish();
+  });
 }
diff --git a/docshell/test/browser/browser_bug655273.js b/docshell/test/browser/browser_bug655273.js
index 7247c5a7acd..a86671c0281 100644
--- a/docshell/test/browser/browser_bug655273.js
+++ b/docshell/test/browser/browser_bug655273.js
@@ -14,9 +14,7 @@ function test() {
   let tab = gBrowser.addTab('http://example.com');
   let tabBrowser = tab.linkedBrowser;
 
-  tabBrowser.addEventListener('load', function(aEvent) {
-    tabBrowser.removeEventListener('load', arguments.callee, true);
-
+  BrowserTestUtils.browserLoaded(tab.linkedBrowser).then(() => {
     let cw = tabBrowser.contentWindow;
     let oldTitle = cw.document.title;
     ok(oldTitle, 'Content window should initially have a title.');
@@ -31,5 +29,5 @@ function test() {
 
     gBrowser.removeTab(tab);
     finish();
-  }, true);
+  });
 }
diff --git a/dom/html/test/browser_bug1108547.js b/dom/html/test/browser_bug1108547.js
index efd64db09f4..a36177e865a 100644
--- a/dom/html/test/browser_bug1108547.js
+++ b/dom/html/test/browser_bug1108547.js
@@ -29,10 +29,9 @@ function runPass(getterFile, finishedCallback) {
 
   // First, set the cookie in a normal window.
   gBrowser.selectedTab = gBrowser.addTab(rootDir + "file_bug1108547-1.html");
-  gBrowser.selectedBrowser.addEventListener("load", afterOpenCookieSetter, true);
+  BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser).then(afterOpenCookieSetter);
 
   function afterOpenCookieSetter() {
-    gBrowser.selectedBrowser.removeEventListener("load", afterOpenCookieSetter, true);
     gBrowser.removeCurrentTab();
 
     // Now, open a private window.
@@ -47,18 +46,21 @@ function runPass(getterFile, finishedCallback) {
     privateWin.gBrowser.tabContainer.addEventListener("TabOpen", onNewTabOpened, true);
   }
 
+  function fetchResult() {
+    return ContentTask.spawn(testBrowser, null, function() {
+      return content.document.getElementById("result").textContent;
+    });
+  }
+
   function onNewTabOpened() {
     // When the new tab is opened, wait for it to load.
     privateWin.gBrowser.tabContainer.removeEventListener("TabOpen", onNewTabOpened, true);
-    privateWin.gBrowser.tabs[privateWin.gBrowser.tabs.length - 1].linkedBrowser.addEventListener("load", onNewTabLoaded, true);
+    BrowserTestUtils.browserLoaded(privateWin.gBrowser.tabs[privateWin.gBrowser.tabs.length - 1].linkedBrowser).then(fetchResult).then(onNewTabLoaded);
   }
 
-  function onNewTabLoaded() {
-    privateWin.gBrowser.tabs[privateWin.gBrowser.tabs.length - 1].linkedBrowser.removeEventListener("load", onNewTabLoaded, true);
-
+  function onNewTabLoaded(result) {
     // Now, ensure that the private tab doesn't have access to the cookie set in normal mode.
-    is(testBrowser.contentDocument.getElementById("result").textContent, "",
-       "Shouldn't have access to the cookies");
+    is(result, "", "Shouldn't have access to the cookies");
 
     // We're done with the private window, close it.
     privateWin.close();
@@ -74,7 +76,7 @@ function runPass(getterFile, finishedCallback) {
   function afterPrivateWindowOpened2() {
     // In the private window, open the setter file, and wait for it to load.
     privateWin.gBrowser.selectedTab = privateWin.gBrowser.addTab(rootDir + "file_bug1108547-1.html");
-    privateWin.gBrowser.selectedBrowser.addEventListener("load", afterOpenCookieSetter2, true);
+    BrowserTestUtils.browserLoaded(privateWin.gBrowser.selectedBrowser).then(afterOpenCookieSetter2);
   }
 
   function afterOpenCookieSetter2() {
@@ -90,15 +92,12 @@ function runPass(getterFile, finishedCallback) {
   function onNewTabOpened2() {
     // When the new tab is opened, wait for it to load.
     gBrowser.tabContainer.removeEventListener("TabOpen", onNewTabOpened2, true);
-    gBrowser.tabs[gBrowser.tabs.length - 1].linkedBrowser.addEventListener("load", onNewTabLoaded2, true);
+    BrowserTestUtils.browserLoaded(gBrowser.tabs[gBrowser.tabs.length - 1].linkedBrowser).then(fetchResult).then(onNewTabLoaded2);
   }
 
-  function onNewTabLoaded2() {
-    gBrowser.tabs[gBrowser.tabs.length - 1].linkedBrowser.removeEventListener("load", onNewTabLoaded2, true);
-
+  function onNewTabLoaded2(result) {
     // Now, ensure that the normal tab doesn't have access to the cookie set in private mode.
-    is(testBrowser.contentDocument.getElementById("result").textContent, "",
-       "Shouldn't have access to the cookies");
+    is(result, "", "Shouldn't have access to the cookies");
 
     // Remove both of the tabs opened here.
     gBrowser.removeCurrentTab();
diff --git a/dom/workers/test/serviceworkers/browser_force_refresh.js b/dom/workers/test/serviceworkers/browser_force_refresh.js
index c6a7d70c3db..5f235f6f5fa 100644
--- a/dom/workers/test/serviceworkers/browser_force_refresh.js
+++ b/dom/workers/test/serviceworkers/browser_force_refresh.js
@@ -12,6 +12,18 @@ function forceRefresh() {
   EventUtils.synthesizeKey('R', { accelKey: true, shiftKey: true });
 }
 
+function frameScript() {
+  function eventHandler(event) {
+    sendAsyncMessage("test:event", {type: event.type});
+  }
+
+  // These are tab-local, so no need to unregister them.
+  addEventListener('base-load', eventHandler, true, true);
+  addEventListener('base-register', eventHandler, true, true);
+  addEventListener('base-sw-ready', eventHandler, true, true);
+  addEventListener('cached-load', eventHandler, true, true);
+}
+
 function test() {
   waitForExplicitFinish();
   SpecialPowers.pushPrefEnv({'set': [['dom.serviceWorkers.enabled', true],
@@ -21,24 +33,29 @@ function test() {
                                      ['dom.caches.enabled', true]]},
                             function() {
     var url = gTestRoot + 'browser_base_force_refresh.html';
-    var tab = gBrowser.addTab(url);
+    var tab = gBrowser.addTab();
     gBrowser.selectedTab = tab;
 
+    tab.linkedBrowser.messageManager.loadFrameScript("data:,(" + encodeURIComponent(frameScript) + ")()", true);
+    gBrowser.loadURI(url);
+
     var cachedLoad = false;
 
-    function eventHandler(event) {
-      if (event.type === 'base-load') {
+    function eventHandler(msg) {
+      if (msg.data.type === 'base-load') {
         if (cachedLoad) {
+          tab.linkedBrowser.messageManager.removeMessageListener("test:event", eventHandler);
+
           gBrowser.removeTab(tab);
           executeSoon(finish);
         }
-      } else if (event.type === 'base-register') {
+      } else if (msg.data.type === 'base-register') {
         ok(!cachedLoad, 'cached load should not occur before base register');
         refresh();
-      } else if (event.type === 'base-sw-ready') {
+      } else if (msg.data.type === 'base-sw-ready') {
         ok(!cachedLoad, 'cached load should not occur before base ready');
         refresh();
-      } else if (event.type === 'cached-load') {
+      } else if (msg.data.type === 'cached-load') {
         ok(!cachedLoad, 'cached load should not occur twice');
         cachedLoad = true;
         forceRefresh();
@@ -47,9 +64,6 @@ function test() {
       return;
     }
 
-    addEventListener('base-load', eventHandler, true, true);
-    addEventListener('base-register', eventHandler, true, true);
-    addEventListener('base-sw-ready', eventHandler, true, true);
-    addEventListener('cached-load', eventHandler, true, true);
+    tab.linkedBrowser.messageManager.addMessageListener("test:event", eventHandler);
   });
 }
diff --git a/toolkit/components/addoncompat/tests/addon/bootstrap.js b/toolkit/components/addoncompat/tests/addon/bootstrap.js
index 8e21ae2fa1c..fe1835d729f 100644
--- a/toolkit/components/addoncompat/tests/addon/bootstrap.js
+++ b/toolkit/components/addoncompat/tests/addon/bootstrap.js
@@ -36,6 +36,17 @@ var gWin;
 var gBrowser;
 var ok, is, info;
 
+function removeTab(tab, done)
+{
+  // Remove the tab in a different turn of the event loop. This way
+  // the nested event loop in removeTab doesn't conflict with the
+  // event listener shims.
+  gWin.setTimeout(() => {
+    gBrowser.removeTab(tab);
+    done();
+  }, 0);
+}
+
 // Make sure that the shims for window.content, browser.contentWindow,
 // and browser.contentDocument are working.
 function testContentWindow()
@@ -56,8 +67,7 @@ function testContentWindow()
       // FIXME: Waiting on bug 1073631.
       //is(browser.contentWindow.wrappedJSObject.global, 3, "global available on document");
 
-      gBrowser.removeTab(tab);
-      resolve();
+      removeTab(tab, resolve);
     });
   });
 }
@@ -108,8 +118,7 @@ function testListeners()
           is(event.target.documentURI, url2, "second load is for second page loaded");
           is(loadWithRemoveCount, 1, "load handler is only called once");
 
-          gBrowser.removeTab(tab);
-          resolve();
+          removeTab(tab, resolve);
         }
       }, true);
 
@@ -162,8 +171,7 @@ function testCapturing()
       gBrowser.removeEventListener("mousedown", capturingHandler, true);
       gBrowser.removeEventListener("mousedown", nonCapturingHandler, false);
 
-      gBrowser.removeTab(tab);
-      resolve();
+      removeTab(tab, resolve);
     });
   });
 }
@@ -194,8 +202,7 @@ function testObserver()
 
         is(observerFired, 1, "got observer notification");
 
-        gBrowser.removeTab(tab);
-        resolve();
+        removeTab(tab, resolve);
       }
     }, true);
   });
@@ -232,8 +239,7 @@ function testSandbox()
       is(browser.contentDocument.getElementById("output").innerHTML, "hello2",
          "EP sandbox code ran successfully");
 
-      gBrowser.removeTab(tab);
-      resolve();
+      removeTab(tab, resolve);
     }, true);
   });
 }
@@ -255,10 +261,8 @@ function testAddonContent()
     let tab = gBrowser.addTab(url);
     let browser = tab.linkedBrowser;
     addLoadListener(browser, function handler() {
-      gBrowser.removeTab(tab);
       res.setSubstitution("addonshim1", null);
-
-      resolve();
+      removeTab(tab, resolve);
     });
   });
 }
@@ -501,9 +505,8 @@ function testAboutModuleRegistration()
 
     addLoadListener(browser, function() {
       testAboutModulesWork(browser).then(() => {
-        gBrowser.removeTab(newTab);
         unregisterModules();
-        resolve();
+        removeTab(newTab, resolve);
       });
     });
   });
@@ -545,10 +548,9 @@ function testProgressListener()
       ok(sawGlobalLocChange, "Saw global onLocationChange");
       ok(sawTabsLocChange, "Saw tabs onLocationChange");
 
-      gBrowser.removeTab(tab);
       gBrowser.removeProgressListener(globalListener);
       gBrowser.removeTabsProgressListener(tabsListener);
-      resolve();
+      removeTab(tab, resolve);
     });
   });
 }
@@ -572,8 +574,7 @@ function testRootTreeItem()
                     .getInterface(Components.interfaces.nsIDOMWindow);
       is(root, gWin, "got correct chrome window");
 
-      gBrowser.removeTab(tab);
-      resolve();
+      removeTab(tab, resolve);
     });
   });
 }
@@ -598,8 +599,7 @@ function testImportNode()
         is(result, node, "got expected import result");
       }
 
-      gBrowser.removeTab(tab);
-      resolve();
+      removeTab(tab, resolve);
     });
   });
 }
diff --git a/toolkit/components/passwordmgr/test/browser/browser_DOMFormHasPassword.js b/toolkit/components/passwordmgr/test/browser/browser_DOMFormHasPassword.js
index 3b1ab552cc6..fbaf064bef6 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_DOMFormHasPassword.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_DOMFormHasPassword.js
@@ -1,82 +1,94 @@
-const HTML_NS = "http://www.w3.org/1999/xhtml";
+const ids = {
+  INPUT_ID: "input1",
+  FORM1_ID: "form1",
+  FORM2_ID: "form2",
+  CHANGE_INPUT_ID: "input2",
+};
 
-const INPUT_ID = "input1";
-const FORM1_ID = "form1";
-const FORM2_ID = "form2";
-const CHANGE_INPUT_ID = "input2";
+function task(ids) {
+  let resolve;
+  let promise = new Promise(r => { resolve = r; });
 
-function test() {
-  waitForExplicitFinish();
-  let tab = gBrowser.selectedTab =
-	gBrowser.addTab("data:text/html;charset=utf-8," +
-			"<html><body>" +
-			"<form id='" + FORM1_ID + "'><input id='" + CHANGE_INPUT_ID + "'></form>" +
-			"<form id='" + FORM2_ID + "'></form>" +
-			"</body></html>");
-  tab.linkedBrowser.addEventListener("load", tabLoad, true);
+  function unexpectedContentEvent(evt) {
+    ok(false, "Received a " + evt.type + " event on content");
+  }
+
+  var gDoc = null;
+
+  addEventListener("load", tabLoad, true);
+
+  function tabLoad() {
+    if (content.location.href == "about:blank")
+      return;
+    removeEventListener("load", tabLoad, true);
+
+    gDoc = content.document;
+    gDoc.addEventListener("DOMFormHasPassword", unexpectedContentEvent, false);
+    gDoc.defaultView.setTimeout(test_inputAdd, 0);
+  }
+
+  function test_inputAdd() {
+    addEventListener("DOMFormHasPassword", test_inputAddHandler, false);
+    let input = gDoc.createElementNS("http://www.w3.org/1999/xhtml", "input");
+    input.setAttribute("type", "password");
+    input.setAttribute("id", ids.INPUT_ID);
+    input.setAttribute("data-test", "unique-attribute");
+    gDoc.getElementById(ids.FORM1_ID).appendChild(input);
+  }
+
+  function test_inputAddHandler(evt) {
+    removeEventListener(evt.type, test_inputAddHandler, false);
+    is(evt.target.id, ids.FORM1_ID,
+       evt.type + " event targets correct form element (added password element)");
+    gDoc.defaultView.setTimeout(test_inputChangeForm, 0);
+  }
+
+  function test_inputChangeForm() {
+    addEventListener("DOMFormHasPassword", test_inputChangeFormHandler, false);
+    let input = gDoc.getElementById(ids.INPUT_ID);
+    input.setAttribute("form", ids.FORM2_ID);
+  }
+
+  function test_inputChangeFormHandler(evt) {
+    removeEventListener(evt.type, test_inputChangeFormHandler, false);
+    is(evt.target.id, ids.FORM2_ID,
+       evt.type + " event targets correct form element (changed form)");
+    gDoc.defaultView.setTimeout(test_inputChangesType, 0);
+  }
+
+  function test_inputChangesType() {
+    addEventListener("DOMFormHasPassword", test_inputChangesTypeHandler, false);
+    let input = gDoc.getElementById(ids.CHANGE_INPUT_ID);
+    input.setAttribute("type", "password");
+  }
+
+  function test_inputChangesTypeHandler(evt) {
+    removeEventListener(evt.type, test_inputChangesTypeHandler, false);
+    is(evt.target.id, ids.FORM1_ID,
+       evt.type + " event targets correct form element (changed type)");
+    gDoc.defaultView.setTimeout(finish, 0);
+  }
+
+  function finish() {
+    gDoc.removeEventListener("DOMFormHasPassword", unexpectedContentEvent, false);
+    resolve();
+  }
+
+  return promise;
 }
 
-function unexpectedContentEvent(evt) {
-  ok(false, "Received a " + evt.type + " event on content");
-}
+add_task(function* () {
+  let tab = gBrowser.selectedTab = gBrowser.addTab();
 
-var gDoc = null;
+  let promise = ContentTask.spawn(tab.linkedBrowser, ids, task);
+  tab.linkedBrowser.loadURI("data:text/html;charset=utf-8," +
+			    "<html><body>" +
+			    "<form id='" + ids.FORM1_ID + "'>" +
+                            "<input id='" + ids.CHANGE_INPUT_ID + "'></form>" +
+			    "<form id='" + ids.FORM2_ID + "'></form>" +
+			    "</body></html>");
+  yield promise;
 
-function tabLoad() {
-  let tab = gBrowser.selectedTab;
-  tab.linkedBrowser.removeEventListener("load", tabLoad, true);
-  gDoc = gBrowser.selectedBrowser.contentDocument;
-  // These events shouldn't escape to content.
-  gDoc.addEventListener("DOMFormHasPassword", unexpectedContentEvent, false);
-  gDoc.defaultView.setTimeout(test_inputAdd, 0);
-}
-
-function test_inputAdd() {
-  gBrowser.addEventListener("DOMFormHasPassword", test_inputAddHandler, false);
-  let input = gDoc.createElementNS(HTML_NS, "input");
-  input.setAttribute("type", "password");
-  input.setAttribute("id", INPUT_ID);
-  input.setAttribute("data-test", "unique-attribute");
-  gDoc.getElementById(FORM1_ID).appendChild(input);
-  info("Done appending the input element");
-}
-
-function test_inputAddHandler(evt) {
-  gBrowser.removeEventListener(evt.type, test_inputAddHandler, false);
-  is(evt.target.id, FORM1_ID,
-     evt.type + " event targets correct form element (added password element)");
-  gDoc.defaultView.setTimeout(test_inputChangeForm, 0);
-}
-
-function test_inputChangeForm() {
-  gBrowser.addEventListener("DOMFormHasPassword", test_inputChangeFormHandler, false);
-  let input = gDoc.getElementById(INPUT_ID);
-  input.setAttribute("form", FORM2_ID);
-}
-
-function test_inputChangeFormHandler(evt) {
-  gBrowser.removeEventListener(evt.type, test_inputChangeFormHandler, false);
-  is(evt.target.id, FORM2_ID,
-     evt.type + " event targets correct form element (changed form)");
-  gDoc.defaultView.setTimeout(test_inputChangesType, 0);
-}
-
-function test_inputChangesType() {
-  gBrowser.addEventListener("DOMFormHasPassword", test_inputChangesTypeHandler, false);
-  let input = gDoc.getElementById(CHANGE_INPUT_ID);
-  input.setAttribute("type", "password");
-}
-
-function test_inputChangesTypeHandler(evt) {
-  gBrowser.removeEventListener(evt.type, test_inputChangesTypeHandler, false);
-  is(evt.target.id, FORM1_ID,
-     evt.type + " event targets correct form element (changed type)");
-  gDoc.defaultView.setTimeout(completeTest, 0);
-}
-
-function completeTest() {
   ok(true, "Test completed");
-  gDoc.removeEventListener("DOMFormHasPassword", unexpectedContentEvent, false);
   gBrowser.removeCurrentTab();
-  finish();
-}
+});
diff --git a/toolkit/components/passwordmgr/test/browser/browser_DOMInputPasswordAdded.js b/toolkit/components/passwordmgr/test/browser/browser_DOMInputPasswordAdded.js
index 50f55da5320..86b57d21d08 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_DOMInputPasswordAdded.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_DOMInputPasswordAdded.js
@@ -1,87 +1,99 @@
-const HTML_NS = "http://www.w3.org/1999/xhtml";
+const consts = {
+  HTML_NS: "http://www.w3.org/1999/xhtml",
 
-const INPUT_ID = "input1";
-const FORM1_ID = "form1";
-const FORM2_ID = "form2";
-const CHANGE_INPUT_ID = "input2";
-const BODY_INPUT_ID = "input3";
+  INPUT_ID: "input1",
+  FORM1_ID: "form1",
+  FORM2_ID: "form2",
+  CHANGE_INPUT_ID: "input2",
+  BODY_INPUT_ID: "input3",
+};
 
-function test() {
-  waitForExplicitFinish();
-  let tab = gBrowser.selectedTab =
-	gBrowser.addTab("data:text/html;charset=utf-8," +
-			"<html><body>" +
-			"<form id='" + FORM1_ID + "'><input id='" + CHANGE_INPUT_ID + "'></form>" +
-			"<form id='" + FORM2_ID + "'></form>" +
-			"</body></html>");
-  tab.linkedBrowser.addEventListener("load", tabLoad, true);
+function task(consts) {
+  let resolve;
+  let promise = new Promise(r => { resolve = r; });
+
+  function unexpectedContentEvent(evt) {
+    ok(false, "Received a " + evt.type + " event on content");
+  }
+
+  var gDoc = null;
+
+  addEventListener("load", tabLoad, true);
+
+  function tabLoad() {
+    removeEventListener("load", tabLoad, true);
+    gDoc = content.document;
+    // These events shouldn't escape to content.
+    gDoc.addEventListener("DOMInputPasswordAdded", unexpectedContentEvent, false);
+    gDoc.defaultView.setTimeout(test_inputAdd, 0);
+  }
+
+  function test_inputAdd() {
+    addEventListener("DOMInputPasswordAdded", test_inputAddHandler, false);
+    let input = gDoc.createElementNS(consts.HTML_NS, "input");
+    input.setAttribute("type", "password");
+    input.setAttribute("id", consts.INPUT_ID);
+    input.setAttribute("data-test", "unique-attribute");
+    gDoc.getElementById(consts.FORM1_ID).appendChild(input);
+    info("Done appending the input element");
+  }
+
+  function test_inputAddHandler(evt) {
+    removeEventListener(evt.type, test_inputAddHandler, false);
+    is(evt.target.id, consts.INPUT_ID,
+       evt.type + " event targets correct input element (added password element)");
+    gDoc.defaultView.setTimeout(test_inputAddOutsideForm, 0);
+  }
+
+  function test_inputAddOutsideForm() {
+    addEventListener("DOMInputPasswordAdded", test_inputAddOutsideFormHandler, false);
+    let input = gDoc.createElementNS(consts.HTML_NS, "input");
+    input.setAttribute("type", "password");
+    input.setAttribute("id", consts.BODY_INPUT_ID);
+    input.setAttribute("data-test", "unique-attribute");
+    gDoc.body.appendChild(input);
+    info("Done appending the input element to the body");
+  }
+
+  function test_inputAddOutsideFormHandler(evt) {
+    removeEventListener(evt.type, test_inputAddOutsideFormHandler, false);
+    is(evt.target.id, consts.BODY_INPUT_ID,
+       evt.type + " event targets correct input element (added password element outside form)");
+    gDoc.defaultView.setTimeout(test_inputChangesType, 0);
+  }
+
+  function test_inputChangesType() {
+    addEventListener("DOMInputPasswordAdded", test_inputChangesTypeHandler, false);
+    let input = gDoc.getElementById(consts.CHANGE_INPUT_ID);
+    input.setAttribute("type", "password");
+  }
+
+  function test_inputChangesTypeHandler(evt) {
+    removeEventListener(evt.type, test_inputChangesTypeHandler, false);
+    is(evt.target.id, consts.CHANGE_INPUT_ID,
+       evt.type + " event targets correct input element (changed type)");
+    gDoc.defaultView.setTimeout(completeTest, 0);
+  }
+
+  function completeTest() {
+    ok(true, "Test completed");
+    gDoc.removeEventListener("DOMInputPasswordAdded", unexpectedContentEvent, false);
+    resolve();
+  }
+
+  return promise;
 }
 
-function unexpectedContentEvent(evt) {
-  ok(false, "Received a " + evt.type + " event on content");
-}
-
-var gDoc = null;
-
-function tabLoad() {
-  let tab = gBrowser.selectedTab;
-  tab.linkedBrowser.removeEventListener("load", tabLoad, true);
-  gDoc = gBrowser.selectedBrowser.contentDocument;
-  // These events shouldn't escape to content.
-  gDoc.addEventListener("DOMInputPasswordAdded", unexpectedContentEvent, false);
-  gDoc.defaultView.setTimeout(test_inputAdd, 0);
-}
-
-function test_inputAdd() {
-  gBrowser.addEventListener("DOMInputPasswordAdded", test_inputAddHandler, false);
-  let input = gDoc.createElementNS(HTML_NS, "input");
-  input.setAttribute("type", "password");
-  input.setAttribute("id", INPUT_ID);
-  input.setAttribute("data-test", "unique-attribute");
-  gDoc.getElementById(FORM1_ID).appendChild(input);
-  info("Done appending the input element");
-}
-
-function test_inputAddHandler(evt) {
-  gBrowser.removeEventListener(evt.type, test_inputAddHandler, false);
-  is(evt.target.id, INPUT_ID,
-     evt.type + " event targets correct input element (added password element)");
-  gDoc.defaultView.setTimeout(test_inputAddOutsideForm, 0);
-}
-
-function test_inputAddOutsideForm() {
-  gBrowser.addEventListener("DOMInputPasswordAdded", test_inputAddOutsideFormHandler, false);
-  let input = gDoc.createElementNS(HTML_NS, "input");
-  input.setAttribute("type", "password");
-  input.setAttribute("id", BODY_INPUT_ID);
-  input.setAttribute("data-test", "unique-attribute");
-  gDoc.body.appendChild(input);
-  info("Done appending the input element to the body");
-}
-
-function test_inputAddOutsideFormHandler(evt) {
-  gBrowser.removeEventListener(evt.type, test_inputAddOutsideFormHandler, false);
-  is(evt.target.id, BODY_INPUT_ID,
-     evt.type + " event targets correct input element (added password element outside form)");
-  gDoc.defaultView.setTimeout(test_inputChangesType, 0);
-}
-
-function test_inputChangesType() {
-  gBrowser.addEventListener("DOMInputPasswordAdded", test_inputChangesTypeHandler, false);
-  let input = gDoc.getElementById(CHANGE_INPUT_ID);
-  input.setAttribute("type", "password");
-}
-
-function test_inputChangesTypeHandler(evt) {
-  gBrowser.removeEventListener(evt.type, test_inputChangesTypeHandler, false);
-  is(evt.target.id, CHANGE_INPUT_ID,
-     evt.type + " event targets correct input element (changed type)");
-  gDoc.defaultView.setTimeout(completeTest, 0);
-}
-
-function completeTest() {
-  ok(true, "Test completed");
-  gDoc.removeEventListener("DOMInputPasswordAdded", unexpectedContentEvent, false);
+add_task(function* () {
+  let tab = gBrowser.selectedTab = gBrowser.addTab();
+  let promise = ContentTask.spawn(tab.linkedBrowser, consts, task);
+  tab.linkedBrowser.loadURI("data:text/html;charset=utf-8," +
+			    "<html><body>" +
+			    "<form id='" + consts.FORM1_ID + "'>" +
+                            "<input id='" + consts.CHANGE_INPUT_ID + "'></form>" +
+			    "<form id='" + consts.FORM2_ID + "'></form>" +
+			    "</body></html>");
+  yield promise;
   gBrowser.removeCurrentTab();
-  finish();
-}
+});
+
diff --git a/toolkit/mozapps/extensions/test/xpinstall/browser_bug611242.js b/toolkit/mozapps/extensions/test/xpinstall/browser_bug611242.js
index 08af331bda2..116fde23454 100644
--- a/toolkit/mozapps/extensions/test/xpinstall/browser_bug611242.js
+++ b/toolkit/mozapps/extensions/test/xpinstall/browser_bug611242.js
@@ -2,15 +2,7 @@
 // Test whether setting a new property in InstallTrigger then persists to other
 // page loads
 function loadURI(aUri, aCallback) {
-  gBrowser.selectedBrowser.addEventListener("load", function() {
-    if (gBrowser.selectedBrowser.currentURI.spec != aUri)
-      return;
-
-    gBrowser.selectedBrowser.removeEventListener("load", arguments.callee, true);
-
-    aCallback();
-  }, true);
-
+  BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser, false, aUri).then(aCallback);
   gBrowser.loadURI(aUri);
 }
 
diff --git a/toolkit/mozapps/extensions/test/xpinstall/browser_enabled.js b/toolkit/mozapps/extensions/test/xpinstall/browser_enabled.js
index 56118c4e1ff..adbec949947 100644
--- a/toolkit/mozapps/extensions/test/xpinstall/browser_enabled.js
+++ b/toolkit/mozapps/extensions/test/xpinstall/browser_enabled.js
@@ -5,20 +5,25 @@ function test() {
 
   gBrowser.selectedTab = gBrowser.addTab();
 
-  function loadListener() {
-    gBrowser.selectedBrowser.removeEventListener("load", loadListener, true);
-    gBrowser.contentWindow.addEventListener("PageLoaded", page_loaded, false);
-  }
+  ContentTask.spawn(gBrowser.selectedBrowser, TESTROOT + "enabled.html", function (url) {
+    return new Promise(resolve => {
+      function page_loaded() {
+        content.removeEventListener("PageLoaded", page_loaded, false);
+        resolve(content.document.getElementById("enabled").textContent);
+      }
 
-  gBrowser.selectedBrowser.addEventListener("load", loadListener, true);
-  gBrowser.loadURI(TESTROOT + "enabled.html");
-}
-
-function page_loaded() {
-  gBrowser.contentWindow.removeEventListener("PageLoaded", page_loaded, false);
-
-  var doc = gBrowser.contentDocument;
-  is(doc.getElementById("enabled").textContent, "true", "installTrigger should have been enabled");
-  gBrowser.removeCurrentTab();
-  finish();
+      function load_listener() {
+        removeEventListener("load", load_listener, true);
+        content.addEventListener("PageLoaded", page_loaded, false);
+      }
+
+      addEventListener("load", load_listener, true);
+
+      content.location.href = url;
+    });
+  }).then(text => {
+    is(text, "true", "installTrigger should have been enabled");
+    gBrowser.removeCurrentTab();
+    finish();
+  });
 }
diff --git a/toolkit/mozapps/extensions/test/xpinstall/browser_enabled2.js b/toolkit/mozapps/extensions/test/xpinstall/browser_enabled2.js
index 290987bdaf7..cc1b8a8b239 100644
--- a/toolkit/mozapps/extensions/test/xpinstall/browser_enabled2.js
+++ b/toolkit/mozapps/extensions/test/xpinstall/browser_enabled2.js
@@ -7,21 +7,26 @@ function test() {
 
   gBrowser.selectedTab = gBrowser.addTab();
 
-  function loadListener() {
-    gBrowser.selectedBrowser.removeEventListener("load", loadListener, true);
-    gBrowser.contentWindow.addEventListener("PageLoaded", page_loaded, false);
-  }
+  ContentTask.spawn(gBrowser.selectedBrowser, TESTROOT + "enabled.html", function (url) {
+    return new Promise(resolve => {
+      function page_loaded() {
+        content.removeEventListener("PageLoaded", page_loaded, false);
+        resolve(content.document.getElementById("enabled").textContent);
+      }
 
-  gBrowser.selectedBrowser.addEventListener("load", loadListener, true);
-  gBrowser.loadURI(TESTROOT + "enabled.html");
-}
-
-function page_loaded() {
-  gBrowser.contentWindow.removeEventListener("PageLoaded", page_loaded, false);
-  Services.prefs.clearUserPref("xpinstall.enabled");
-
-  var doc = gBrowser.contentDocument;
-  is(doc.getElementById("enabled").textContent, "false", "installTrigger should have not been enabled");
-  gBrowser.removeCurrentTab();
-  finish();
+      function load_listener() {
+        removeEventListener("load", load_listener, true);
+        content.addEventListener("PageLoaded", page_loaded, false);
+      }
+
+      addEventListener("load", load_listener, true);
+
+      content.location.href = url;
+    });
+  }).then(text => {
+    is(text, "false", "installTrigger should have not been enabled");
+    Services.prefs.clearUserPref("xpinstall.enabled");
+    gBrowser.removeCurrentTab();
+    finish();
+  });
 }
diff --git a/toolkit/mozapps/extensions/test/xpinstall/browser_enabled3.js b/toolkit/mozapps/extensions/test/xpinstall/browser_enabled3.js
index ea3eba5304c..4cb6fe37bf5 100644
--- a/toolkit/mozapps/extensions/test/xpinstall/browser_enabled3.js
+++ b/toolkit/mozapps/extensions/test/xpinstall/browser_enabled3.js
@@ -13,13 +13,28 @@ function test() {
   }));
   gBrowser.selectedTab = gBrowser.addTab();
 
-  function loadListener() {
-    gBrowser.selectedBrowser.removeEventListener("load", loadListener, true);
-    gBrowser.contentWindow.addEventListener("InstallTriggered", page_loaded, false);
-  }
+  ContentTask.spawn(gBrowser.selectedBrowser, TESTROOT + "installtrigger.html?" + triggers, url => {
+    return new Promise(resolve => {
+      function page_loaded() {
+        content.removeEventListener("PageLoaded", page_loaded, false);
+        resolve(content.document.getElementById("return").textContent);
+      }
 
-  gBrowser.selectedBrowser.addEventListener("load", loadListener, true);
-  gBrowser.loadURI(TESTROOT + "installtrigger.html?" + triggers);
+      function load_listener() {
+        removeEventListener("load", load_listener, true);
+        content.addEventListener("InstallTriggered", page_loaded, false);
+      }
+
+      addEventListener("load", load_listener, true);
+
+      content.location.href = url;
+    });
+  }).then(text => {
+    is(text, "false", "installTrigger should have not been enabled");
+    Services.prefs.clearUserPref("xpinstall.enabled");
+    gBrowser.removeCurrentTab();
+    Harness.finish();
+  });
 }
 
 function install_disabled(installInfo) {
@@ -35,14 +50,3 @@ function confirm_install(window) {
   ok(false, "Should never see an install confirmation dialog");
   return false;
 }
-
-function page_loaded() {
-  gBrowser.contentWindow.removeEventListener("InstallTriggered", page_loaded, false);
-  Services.prefs.clearUserPref("xpinstall.enabled");
-
-  var doc = gBrowser.contentDocument;
-  is(doc.getElementById("return").textContent, "false", "installTrigger should have not been enabled");
-  gBrowser.removeCurrentTab();
-  Harness.finish();
-}
-// ----------------------------------------------------------------------------
diff --git a/toolkit/mozapps/extensions/test/xpinstall/browser_offline.js b/toolkit/mozapps/extensions/test/xpinstall/browser_offline.js
index 54032c8a43a..8a16a6a807c 100644
--- a/toolkit/mozapps/extensions/test/xpinstall/browser_offline.js
+++ b/toolkit/mozapps/extensions/test/xpinstall/browser_offline.js
@@ -34,8 +34,9 @@ function finish_test(count) {
     info("Checking if the browser is still offline...");
 
     let tab = gBrowser.selectedTab;
-    tab.linkedBrowser.addEventListener("DOMContentLoaded", function errorLoad() {
-      tab.linkedBrowser.removeEventListener("DOMContentLoaded", errorLoad, true);
+    ContentTask.spawn(tab.linkedBrowser, null, () => {
+      return ContentTaskUtils.waitForEvent(this, "DOMContentLoaded", true);
+    }).then(() => {
       let url = tab.linkedBrowser.contentDocument.documentURI;
       info("loaded: " + url);
       if (/^about:neterror\?e=netOffline/.test(url)) {
@@ -44,7 +45,7 @@ function finish_test(count) {
         gBrowser.removeCurrentTab();
         Harness.finish();
       }
-    }, true);
+    });
     tab.linkedBrowser.loadURI("http://example.com/");
   }