diff --git a/dom/workers/URL.cpp b/dom/workers/URL.cpp
index c1220fbab2c..2bb0f2802c4 100644
--- a/dom/workers/URL.cpp
+++ b/dom/workers/URL.cpp
@@ -144,7 +144,7 @@ public:
 
       principal = doc->NodePrincipal();
     } else {
-      MOZ_ASSERT(mWorkerPrivate->IsChromeWorker());
+      MOZ_ASSERT_IF(!mWorkerPrivate->GetParent(), mWorkerPrivate->IsChromeWorker());
       principal = mWorkerPrivate->GetPrincipal();
     }
 
@@ -199,7 +199,7 @@ public:
 
       principal = doc->NodePrincipal();
     } else {
-      MOZ_ASSERT(mWorkerPrivate->IsChromeWorker());
+      MOZ_ASSERT_IF(!mWorkerPrivate->GetParent(), mWorkerPrivate->IsChromeWorker());
       principal = mWorkerPrivate->GetPrincipal();
     }
 
diff --git a/dom/workers/test/Makefile.in b/dom/workers/test/Makefile.in
index fa969da9c7d..741d7048f1c 100644
--- a/dom/workers/test/Makefile.in
+++ b/dom/workers/test/Makefile.in
@@ -144,7 +144,7 @@ MOCHITEST_CHROME_FILES = \
   dom_worker_helper.js \
   test_bug883784.xul \
   test_bug883784.jsm \
-  url_worker.js \
+  jsm_url_worker.js \
   $(NULL)
 
 include $(topsrcdir)/config/rules.mk
diff --git a/dom/workers/test/jsm_url_worker.js b/dom/workers/test/jsm_url_worker.js
new file mode 100644
index 00000000000..05667993d40
--- /dev/null
+++ b/dom/workers/test/jsm_url_worker.js
@@ -0,0 +1,82 @@
+onmessage = function(event) {
+  if (event.data != 0) {
+    var worker = new Worker('jsm_url_worker.js');
+    worker.onmessage = function(event) {
+      postMessage(event.data);
+    }
+
+    worker.postMessage(event.data - 1);
+    return;
+  }
+
+  status = false;
+  try {
+    if ((URL instanceof Object)) {
+      status = true;
+    }
+  } catch(e) {
+  }
+
+  postMessage({type: 'status', status: status, msg: 'URL object:' + URL});
+
+  status = false;
+  var blob = null;
+  try {
+    blob = new Blob([]);
+    status = true;
+  } catch(e) {
+  }
+
+  postMessage({type: 'status', status: status, msg: 'Blob:' + blob});
+
+  status = false;
+  var url = null;
+  try {
+    url = URL.createObjectURL(blob);
+    status = true;
+  } catch(e) {
+  }
+
+  postMessage({type: 'status', status: status, msg: 'Blob URL:' + url});
+
+  status = false;
+  try {
+    URL.revokeObjectURL(url);
+    status = true;
+  } catch(e) {
+  }
+
+  postMessage({type: 'status', status: status, msg: 'Blob Revoke URL'});
+
+  status = false;
+  var url = null;
+  try {
+    url = URL.createObjectURL(true);
+  } catch(e) {
+    status = true;
+  }
+
+  postMessage({type: 'status', status: status, msg: 'CreateObjectURL should fail if the arg is not a blob'});
+
+  status = false;
+  var url = null;
+  try {
+    url = URL.createObjectURL(blob);
+    status = true;
+  } catch(e) {
+  }
+
+  postMessage({type: 'status', status: status, msg: 'Blob URL2:' + url});
+  postMessage({type: 'url', url: url});
+
+  status = false;
+  try {
+    URL.createObjectURL(new Object());
+  } catch(e) {
+    status = true;
+  }
+
+  postMessage({type: 'status', status: status, msg: 'Exception wanted' });
+
+  postMessage({type: 'finish' });
+}
diff --git a/dom/workers/test/test_bug883784.jsm b/dom/workers/test/test_bug883784.jsm
index 40066af0409..096272d3169 100644
--- a/dom/workers/test/test_bug883784.jsm
+++ b/dom/workers/test/test_bug883784.jsm
@@ -2,7 +2,7 @@ this.EXPORTED_SYMBOLS = ["Test"];
 
 this.Test = {
   start: function(ok, is, finish) {
-    let worker = new ChromeWorker("url_worker.js");
+    let worker = new ChromeWorker("jsm_url_worker.js");
     worker.onmessage = function(event) {
 
       if (event.data.type == 'finish') {
@@ -30,6 +30,6 @@ this.Test = {
       finish();
     };
 
-    worker.postMessage(true);
+    worker.postMessage(0);
   }
 };
diff --git a/dom/workers/test/test_url.html b/dom/workers/test/test_url.html
index 0ce5976c2a3..3dc679709b9 100644
--- a/dom/workers/test/test_url.html
+++ b/dom/workers/test/test_url.html
@@ -21,7 +21,7 @@
     is(event.target, worker);
 
     if (event.data.type == 'finish') {
-      SimpleTest.finish();
+      runTest();
     } else if (event.data.type == 'status') {
       ok(event.data.status, event.data.msg);
     } else if (event.data.type == 'url') {
@@ -42,8 +42,22 @@
     SimpleTest.finish();
   };
 
-  worker.postMessage(true);
+  var tests = [
+    function() { worker.postMessage(0); },
+    function() { worker.postMessage(1); }
+  ];
 
+  function runTest() {
+    if (!tests.length) {
+      SimpleTest.finish();
+      return;
+    }
+
+    var test = tests.shift();
+    test();
+  }
+
+  runTest();
   SimpleTest.waitForExplicitFinish();
 
 </script>
diff --git a/dom/workers/test/url_worker.js b/dom/workers/test/url_worker.js
index 0c7c2d8b930..4d8c84fc610 100644
--- a/dom/workers/test/url_worker.js
+++ b/dom/workers/test/url_worker.js
@@ -1,4 +1,14 @@
-onmessage = function() {
+onmessage = function(event) {
+  if (event.data != 0) {
+    var worker = new Worker('url_worker.js');
+    worker.onmessage = function(event) {
+      postMessage(event.data);
+    }
+
+    worker.postMessage(event.data - 1);
+    return;
+  }
+
   status = false;
   try {
     if ((URL instanceof Object)) {