diff --git a/browser/devtools/debugger/debugger-controller.js b/browser/devtools/debugger/debugger-controller.js
index 0b055de5ffc..3070179f391 100644
--- a/browser/devtools/debugger/debugger-controller.js
+++ b/browser/devtools/debugger/debugger-controller.js
@@ -185,7 +185,6 @@ let DebuggerController = {
     if (this._target.isTabActor) {
       this.Workers.disconnect();
     }
-    this.Tracer.disconnect();
     this.disconnect();
 
     this._shutdown = true;
@@ -204,7 +203,7 @@ let DebuggerController = {
     }
 
     let target = this._target;
-    let { client, form: { chromeDebugger, traceActor, actor } } = target;
+    let { client, form: { chromeDebugger, actor } } = target;
     target.on("close", this._onTabDetached);
     target.on("navigate", this._onTabNavigated);
     target.on("will-navigate", this._onTabNavigated);
@@ -218,10 +217,6 @@ let DebuggerController = {
       yield this._startChromeDebugging(chromeDebugger);
     } else {
       yield this._startDebuggingTab();
-
-      if (Prefs.tracerEnabled && traceActor) {
-        yield this._startTracingTab(traceActor);
-      }
     }
 
     this._hideUnsupportedFeatures();
@@ -390,31 +385,6 @@ let DebuggerController = {
     return deferred.promise;
   },
 
-  /**
-   * Sets up an execution tracing session.
-   *
-   * @param object aTraceActor
-   *        The remote protocol grip of the trace actor.
-   * @return object
-   *         A promise resolved once the client attaches to the tracer.
-   */
-  _startTracingTab: function(aTraceActor) {
-    let deferred = promise.defer();
-
-    this.client.attachTracer(aTraceActor, (response, traceClient) => {
-      if (!traceClient) {
-        deferred.reject(new Error("Failed to attach to tracing actor."));
-        return;
-      }
-      this.traceClient = traceClient;
-      this.Tracer.connect();
-
-      deferred.resolve();
-    });
-
-    return deferred.promise;
-  },
-
   /**
    * Detach and reattach to the thread actor with useSourceMaps true, blow
    * away old sources and get them again.
@@ -1301,7 +1271,6 @@ SourceScripts.prototype = {
     // both in the editor and the breakpoints pane.
     DebuggerController.Breakpoints.updatePaneBreakpoints();
     DebuggerController.Breakpoints.updateEditorBreakpoints();
-    DebuggerController.HitCounts.updateEditorHitCounts();
 
     // Make sure the events listeners are up to date.
     if (DebuggerView.instrumentsPaneTab == "events-tab") {
@@ -1354,7 +1323,6 @@ SourceScripts.prototype = {
     // both in the editor and the breakpoints pane.
     DebuggerController.Breakpoints.updatePaneBreakpoints();
     DebuggerController.Breakpoints.updateEditorBreakpoints();
-    DebuggerController.HitCounts.updateEditorHitCounts();
 
     // Signal that sources have been added.
     window.emit(EVENTS.SOURCES_ADDED);
@@ -1566,237 +1534,6 @@ SourceScripts.prototype = {
   }
 };
 
-/**
- * Tracer update the UI according to the messages exchanged with the tracer
- * actor.
- */
-function Tracer() {
-  this._trace = null;
-  this._idCounter = 0;
-  this.onTraces = this.onTraces.bind(this);
-}
-
-Tracer.prototype = {
-  get client() {
-    return DebuggerController.client;
-  },
-
-  get traceClient() {
-    return DebuggerController.traceClient;
-  },
-
-  get tracing() {
-    return !!this._trace;
-  },
-
-  /**
-   * Hooks up the debugger controller with the tracer client.
-   */
-  connect: function() {
-    this._stack = [];
-    this.client.addListener("traces", this.onTraces);
-  },
-
-  /**
-   * Disconnects the debugger controller from the tracer client. Any further
-   * communcation with the tracer actor will not have any effect on the UI.
-   */
-  disconnect: function() {
-    this._stack = null;
-    this.client.removeListener("traces", this.onTraces);
-  },
-
-  /**
-   * Instructs the tracer actor to start tracing.
-   */
-  startTracing: function(aCallback = () => {}) {
-    if (this.tracing) {
-      return;
-    }
-
-    DebuggerView.Tracer.selectTab();
-
-    let id = this._trace = "dbg.trace" + Math.random();
-    let fields = [
-      "name",
-      "location",
-      "hitCount",
-      "parameterNames",
-      "depth",
-      "arguments",
-      "return",
-      "throw",
-      "yield"
-    ];
-
-    this.traceClient.startTrace(fields, id, aResponse => {
-      const { error } = aResponse;
-      if (error) {
-        DevToolsUtils.reportException("Tracer.prototype.startTracing", error);
-        this._trace = null;
-      }
-
-      aCallback(aResponse);
-    });
-  },
-
-  /**
-   * Instructs the tracer actor to stop tracing.
-   */
-  stopTracing: function(aCallback = () => {}) {
-    if (!this.tracing) {
-      return;
-    }
-    this.traceClient.stopTrace(this._trace, aResponse => {
-      const { error } = aResponse;
-      if (error) {
-        DevToolsUtils.reportException("Tracer.prototype.stopTracing", error);
-      }
-
-      this._trace = null;
-      DebuggerController.HitCounts.clear();
-      aCallback(aResponse);
-    });
-  },
-
-  onTraces: function (aEvent, { traces }) {
-    const tracesLength = traces.length;
-    let tracesToShow;
-
-    // Update hit counts.
-    for (let t of traces) {
-      if (t.type == "enteredFrame") {
-        DebuggerController.HitCounts.set(t.location, t.hitCount);
-      }
-    }
-    DebuggerController.HitCounts.updateEditorHitCounts();
-
-    // Limit number of traces to be shown in the log.
-    if (tracesLength > TracerView.MAX_TRACES) {
-      tracesToShow = traces.slice(tracesLength - TracerView.MAX_TRACES, tracesLength);
-      this._stack.splice(0, this._stack.length);
-      DebuggerView.Tracer.empty();
-    } else {
-      tracesToShow = traces;
-    }
-
-    // Show traces in the log.
-    for (let t of tracesToShow) {
-      if (t.type == "enteredFrame") {
-        this._onCall(t);
-      } else {
-        this._onReturn(t);
-      }
-    }
-    DebuggerView.Tracer.commit();
-  },
-
-  /**
-   * Callback for handling a new call frame.
-   */
-  _onCall: function({ name, location, blackBoxed, parameterNames, depth, arguments: args }) {
-    const item = {
-      name: name,
-      location: location,
-      id: this._idCounter++,
-      blackBoxed
-    };
-
-    this._stack.push(item);
-    DebuggerView.Tracer.addTrace({
-      type: "call",
-      name: name,
-      location: location,
-      depth: depth,
-      parameterNames: parameterNames,
-      arguments: args,
-      frameId: item.id,
-      blackBoxed
-    });
-  },
-
-  /**
-   * Callback for handling an exited frame.
-   */
-  _onReturn: function(aPacket) {
-    if (!this._stack.length) {
-      return;
-    }
-
-    const { name, id, location, blackBoxed } = this._stack.pop();
-    DebuggerView.Tracer.addTrace({
-      type: aPacket.why,
-      name: name,
-      location: location,
-      depth: aPacket.depth,
-      frameId: id,
-      returnVal: aPacket.return || aPacket.throw || aPacket.yield,
-      blackBoxed
-    });
-  },
-
-  /**
-   * Create an object which has the same interface as a normal object client,
-   * but since we already have all the information for an object that we will
-   * ever get (the server doesn't create actors when tracing, just firehoses
-   * data and forgets about it) just return the data immdiately.
-   *
-   * @param Object aObject
-   *        The tracer object "grip" (more like a limited snapshot).
-   * @returns Object
-   *          The synchronous client object.
-   */
-  syncGripClient: function(aObject) {
-    return {
-      get isFrozen() { return aObject.frozen; },
-      get isSealed() { return aObject.sealed; },
-      get isExtensible() { return aObject.extensible; },
-
-      get ownProperties() { return aObject.ownProperties; },
-      get prototype() { return null; },
-
-      getParameterNames: callback => callback(aObject),
-      getPrototypeAndProperties: callback => callback(aObject),
-      getPrototype: callback => callback(aObject),
-
-      getOwnPropertyNames: (callback) => {
-        callback({
-          ownPropertyNames: aObject.ownProperties
-            ? Object.keys(aObject.ownProperties)
-            : []
-        });
-      },
-
-      getProperty: (property, callback) => {
-        callback({
-          descriptor: aObject.ownProperties
-            ? aObject.ownProperties[property]
-            : null
-        });
-      },
-
-      getDisplayString: callback => callback("[object " + aObject.class + "]"),
-
-      getScope: callback => callback({
-        error: "scopeNotAvailable",
-        message: "Cannot get scopes for traced objects"
-      })
-    };
-  },
-
-  /**
-   * Wraps object snapshots received from the tracer server so that we can
-   * differentiate them from long living object grips from the debugger server
-   * in the variables view.
-   *
-   * @param Object aObject
-   *        The object snapshot from the tracer actor.
-   */
-  WrappedObject: function(aObject) {
-    this.object = aObject;
-  }
-};
-
 /**
  * Handles breaking on event listeners in the currently debugged target.
  */
@@ -2167,10 +1904,10 @@ Breakpoints.prototype = {
         }
       }
 
-      // Preserve information about the breakpoint's line text, to display it
-      // in the sources pane without requiring fetching the source (for example,
-      // after the target navigated). Note that this will get out of sync
-      // if the source text contents change.
+      // Preserve information about the breakpoint's line text, to display it in
+      // the sources pane without requiring fetching the source (for example,
+      // after the target navigated). Note that this will get out of sync if the
+      // source text contents change.
       let line = aBreakpointClient.location.line - 1;
       aBreakpointClient.text = DebuggerView.editor.getText(line).trim();
 
@@ -2427,87 +2164,6 @@ Object.defineProperty(Breakpoints.prototype, "_addedOrDisabled", {
   }
 });
 
-/**
- * Handles Tracer's hit counts.
- */
-function HitCounts() {
-  /**
-   * Storage of hit counts for every location
-   * hitCount = _locations[url][line][column]
-   */
-  this._hitCounts = Object.create(null);
-}
-
-HitCounts.prototype = {
-  set: function({url, line, column}, aHitCount) {
-    if (url) {
-      if (!this._hitCounts[url]) {
-        this._hitCounts[url] = Object.create(null);
-      }
-      if (!this._hitCounts[url][line]) {
-        this._hitCounts[url][line] = Object.create(null);
-      }
-      this._hitCounts[url][line][column] = aHitCount;
-    }
-  },
-
-  /**
-   * Update all the hit counts in the editor view. This is invoked when the
-   * selected script is changed, or when new sources are received via the
-   * _onNewSource and _onSourcesAdded event listeners.
-   */
-  updateEditorHitCounts: function() {
-    // First, remove all hit counters.
-    DebuggerView.editor.removeAllMarkers("hit-counts");
-
-    // Then, add new hit counts, just for the current source.
-    for (let url in this._hitCounts) {
-      for (let line in this._hitCounts[url]) {
-        for (let column in this._hitCounts[url][line]) {
-          this._updateEditorHitCount({url, line, column});
-        }
-      }
-    }
-  },
-
-  /**
-   * Update a hit counter on a certain line.
-   */
-  _updateEditorHitCount: function({url, line, column}) {
-    // Editor must be initialized.
-    if (!DebuggerView.editor) {
-      return;
-    }
-
-    // No need to do anything if the counter's source is not being shown in the
-    // editor.
-    if (url &&
-        DebuggerView.Sources.selectedItem.attachment.source.url != url) {
-      return;
-    }
-
-    // There might be more counters on the same line. We need to combine them
-    // into one.
-    let content = Object.keys(this._hitCounts[url][line])
-                    .sort() // Sort by key (column).
-                    .map(a => this._hitCounts[url][line][a]) // Extract values.
-                    .map(a => a + "\u00D7") // Format hit count (e.g. 146×).
-                    .join("|");
-
-    // CodeMirror's lines are indexed from 0, while traces start from 1
-    DebuggerView.editor.addContentMarker(line - 1, "hit-counts", "hit-count",
-                                         content);
-  },
-
-  /**
-   * Remove all hit couters and clear the storage
-   */
-  clear: function() {
-    DebuggerView.editor.removeAllMarkers("hit-counts");
-    this._hitCounts = Object.create(null);
-  }
-}
-
 /**
  * Localization convenience methods.
  */
@@ -2528,7 +2184,6 @@ let Prefs = new ViewHelpers.Prefs("devtools", {
   sourceMapsEnabled: ["Bool", "debugger.source-maps-enabled"],
   prettyPrintEnabled: ["Bool", "debugger.pretty-print-enabled"],
   autoPrettyPrint: ["Bool", "debugger.auto-pretty-print"],
-  tracerEnabled: ["Bool", "debugger.tracer"],
   workersEnabled: ["Bool", "debugger.workers"],
   editorTabSize: ["Int", "editor.tabsize"],
   autoBlackBox: ["Bool", "debugger.auto-black-box"]
@@ -2550,8 +2205,6 @@ DebuggerController.StackFrames = new StackFrames();
 DebuggerController.SourceScripts = new SourceScripts();
 DebuggerController.Breakpoints = new Breakpoints();
 DebuggerController.Breakpoints.DOM = new EventListeners();
-DebuggerController.Tracer = new Tracer();
-DebuggerController.HitCounts = new HitCounts();
 
 /**
  * Export some properties to the global scope for easier access.
diff --git a/browser/devtools/debugger/debugger-view.js b/browser/devtools/debugger/debugger-view.js
index c19ebd52307..d3cdaf7a39e 100644
--- a/browser/devtools/debugger/debugger-view.js
+++ b/browser/devtools/debugger/debugger-view.js
@@ -58,7 +58,6 @@ let DebuggerView = {
     this.Workers.initialize();
     this.Sources.initialize();
     this.VariableBubble.initialize();
-    this.Tracer.initialize();
     this.WatchExpressions.initialize();
     this.EventListeners.initialize();
     this.GlobalSearch.initialize();
@@ -91,7 +90,6 @@ let DebuggerView = {
     this.StackFramesClassicList.destroy();
     this.Sources.destroy();
     this.VariableBubble.destroy();
-    this.Tracer.destroy();
     this.WatchExpressions.destroy();
     this.EventListeners.destroy();
     this.GlobalSearch.destroy();
@@ -174,9 +172,7 @@ let DebuggerView = {
     VariablesViewController.attach(this.Variables, {
       getEnvironmentClient: aObject => gThreadClient.environment(aObject),
       getObjectClient: aObject => {
-        return aObject instanceof DebuggerController.Tracer.WrappedObject
-          ? DebuggerController.Tracer.syncGripClient(aObject.object)
-          : gThreadClient.pauseGrip(aObject)
+        return gThreadClient.pauseGrip(aObject)
       }
     });
 
@@ -219,9 +215,6 @@ let DebuggerView = {
     }
 
     let gutters = ["breakpoints"];
-    if (Services.prefs.getBoolPref("devtools.debugger.tracer")) {
-      gutters.unshift("hit-counts");
-    }
 
     this.editor = new Editor({
       mode: Editor.modes.text,
@@ -414,7 +407,6 @@ let DebuggerView = {
       // source.
       DebuggerView.Sources.selectedValue = aSource.actor;
       DebuggerController.Breakpoints.updateEditorBreakpoints();
-      DebuggerController.HitCounts.updateEditorHitCounts();
 
       histogram.add(Date.now() - startTime);
 
@@ -673,7 +665,6 @@ let DebuggerView = {
   GlobalSearch: null,
   StackFrames: null,
   Sources: null,
-  Tracer: null,
   Variables: null,
   VariableBubble: null,
   WatchExpressions: null,
diff --git a/browser/devtools/debugger/debugger.xul b/browser/devtools/debugger/debugger.xul
index 9d7f5aa2feb..ac559e1f09e 100644
--- a/browser/devtools/debugger/debugger.xul
+++ b/browser/devtools/debugger/debugger.xul
@@ -31,7 +31,6 @@
   <script type="text/javascript" src="debugger/workers-view.js"/>
   <script type="text/javascript" src="debugger/sources-view.js"/>
   <script type="text/javascript" src="debugger/variable-bubble-view.js"/>
-  <script type="text/javascript" src="debugger/tracer-view.js"/>
   <script type="text/javascript" src="debugger/watch-expressions-view.js"/>
   <script type="text/javascript" src="debugger/event-listeners-view.js"/>
   <script type="text/javascript" src="debugger/global-search-view.js"/>
@@ -280,13 +279,6 @@
                        class="devtools-toolbarbutton"
                        tabindex="0"/>
       </hbox>
-      <hbox>
-        <toolbarbutton id="trace"
-                       class="devtools-toolbarbutton"
-                       command="toggleTracing"
-                       tabindex="0"
-                       hidden="true"/>
-      </hbox>
       <vbox id="stackframes" flex="1"/>
       <textbox id="searchbox"
                class="devtools-searchinput" type="search"/>
@@ -324,7 +316,6 @@
           <tabs>
             <tab id="sources-tab" label="&debuggerUI.tabs.sources;"/>
             <tab id="callstack-tab" label="&debuggerUI.tabs.callstack;"/>
-            <tab id="tracer-tab" label="&debuggerUI.tabs.traces;" hidden="true"/>
           </tabs>
           <tabpanels flex="1">
             <tabpanel id="sources-tabpanel">
@@ -355,26 +346,6 @@
             <tabpanel id="callstack-tabpanel">
               <vbox id="callstack-list" flex="1"/>
             </tabpanel>
-            <tabpanel id="tracer-tabpanel">
-              <vbox id="tracer-traces" flex="1"/>
-              <hbox class="trace-item-template" hidden="true">
-                <hbox class="trace-item" align="center" flex="1" crop="end">
-                  <label class="trace-type plain"/>
-                  <label class="trace-name plain" crop="end"/>
-                </hbox>
-              </hbox>
-              <toolbar id="tracer-toolbar" class="devtools-toolbar">
-                <toolbarbutton id="clear-tracer"
-                               label="&debuggerUI.clearButton;"
-                               tooltiptext="&debuggerUI.clearButton.tooltip;"
-                               command="clearTraces"
-                               class="devtools-toolbarbutton"/>
-                <textbox id="tracer-search"
-                         class="devtools-searchinput"
-                         flex="1"
-                         type="search"/>
-              </toolbar>
-            </tabpanel>
           </tabpanels>
         </tabbox>
       </vbox>
diff --git a/browser/devtools/debugger/test/browser.ini b/browser/devtools/debugger/test/browser.ini
index 858996f5ca3..018cbaaef23 100644
--- a/browser/devtools/debugger/test/browser.ini
+++ b/browser/devtools/debugger/test/browser.ini
@@ -33,7 +33,6 @@ support-files =
   code_script-switching-01.js
   code_script-switching-02.js
   code_test-editor-mode
-  code_tracing-01.js
   code_ugly.js
   code_ugly-2.js
   code_ugly-3.js
@@ -91,7 +90,6 @@ support-files =
   doc_promise.html
   doc_random-javascript.html
   doc_recursion-stack.html
-  doc_same-line-functions.html
   doc_scope-variable.html
   doc_scope-variable-2.html
   doc_scope-variable-3.html
@@ -103,7 +101,6 @@ support-files =
   doc_split-console-paused-reload.html
   doc_step-out.html
   doc_terminate-on-tab-close.html
-  doc_tracing-01.html
   doc_watch-expressions.html
   doc_watch-expression-button.html
   doc_with-frame.html
@@ -247,10 +244,6 @@ skip-if = e10s && debug
 skip-if = e10s # TODO
 [browser_dbg_hide-toolbar-buttons.js]
 skip-if = e10s
-[browser_dbg_hit-counts-01.js]
-skip-if = e10s && debug
-[browser_dbg_hit-counts-02.js]
-skip-if = e10s && debug
 [browser_dbg_host-layout.js]
 skip-if = e10s && debug
 [browser_dbg_iframes.js]
@@ -453,22 +446,6 @@ skip-if = e10s # TODO
 skip-if = e10s # TODO
 [browser_dbg_terminate-on-tab-close.js]
 skip-if = e10s && debug
-[browser_dbg_tracing-01.js]
-skip-if = e10s && debug
-[browser_dbg_tracing-02.js]
-skip-if = e10s && debug
-[browser_dbg_tracing-03.js]
-skip-if = e10s && debug
-[browser_dbg_tracing-04.js]
-skip-if = e10s && debug
-[browser_dbg_tracing-05.js]
-skip-if = e10s && debug
-[browser_dbg_tracing-06.js]
-skip-if = e10s && debug
-[browser_dbg_tracing-07.js]
-skip-if = e10s && debug
-[browser_dbg_tracing-08.js]
-skip-if = e10s && debug
 [browser_dbg_variables-view-01.js]
 skip-if = e10s && debug
 [browser_dbg_variables-view-02.js]
diff --git a/browser/devtools/debugger/test/browser_dbg_hit-counts-01.js b/browser/devtools/debugger/test/browser_dbg_hit-counts-01.js
deleted file mode 100644
index 9ea03c310ef..00000000000
--- a/browser/devtools/debugger/test/browser_dbg_hit-counts-01.js
+++ /dev/null
@@ -1,61 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-/**
- * Evaluating two functions on the same line and checking for correct hit count
- * for both of them in CodeMirror's gutter.
- */
-
-const TAB_URL = EXAMPLE_URL + "doc_same-line-functions.html";
-const CODE_URL = "code_same-line-functions.js";
-
-let gTab, gPanel, gDebugger;
-let gEditor;
-
-function test() {
-  Task.async(function* () {
-    yield pushPrefs(["devtools.debugger.tracer", true]);
-
-    initDebugger(TAB_URL).then(([aTab,, aPanel]) => {
-      gTab = aTab;
-      gPanel = aPanel;
-      gDebugger = gPanel.panelWin;
-      gEditor = gDebugger.DebuggerView.editor;
-
-      Task.async(function* () {
-        yield waitForSourceShown(gPanel, CODE_URL);
-        yield startTracing(gPanel);
-
-        clickButton();
-
-        yield waitForClientEvents(aPanel, "traces");
-
-        testHitCounts();
-
-        yield stopTracing(gPanel);
-        yield popPrefs();
-        yield closeDebuggerAndFinish(gPanel);
-      })();
-    });
-  })().catch(e => {
-    ok(false, "Got an error: " + e.message + "\n" + e.stack);
-  });
-}
-
-function clickButton() {
-  generateMouseClickInTab(gTab, "content.document.querySelector('button')");
-}
-
-function testHitCounts() {
-  let marker = gEditor.getMarker(0, 'hit-counts');
-
-  is(marker.innerHTML, "1\u00D7|1\u00D7",
-    "Both functions should be hit only once.");
-}
-
-registerCleanupFunction(function() {
-  gTab = null;
-  gPanel = null;
-  gDebugger = null;
-  gEditor = null;
-});
diff --git a/browser/devtools/debugger/test/browser_dbg_hit-counts-02.js b/browser/devtools/debugger/test/browser_dbg_hit-counts-02.js
deleted file mode 100644
index 6cff1e45c80..00000000000
--- a/browser/devtools/debugger/test/browser_dbg_hit-counts-02.js
+++ /dev/null
@@ -1,66 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-/**
- * When tracing is stopped all hit counters should be cleared.
- */
-
-const TAB_URL = EXAMPLE_URL + "doc_same-line-functions.html";
-const CODE_URL = "code_same-line-functions.js";
-
-let gTab, gPanel, gDebugger;
-let gEditor;
-
-function test() {
-  Task.async(function* () {
-    yield pushPrefs(["devtools.debugger.tracer", true]);
-
-    initDebugger(TAB_URL).then(([aTab,, aPanel]) => {
-      gTab = aTab;
-      gPanel = aPanel;
-      gDebugger = gPanel.panelWin;
-      gEditor = gDebugger.DebuggerView.editor;
-
-      Task.async(function* () {
-        yield waitForSourceShown(gPanel, CODE_URL);
-        yield startTracing(gPanel);
-
-        clickButton();
-
-        yield waitForClientEvents(aPanel, "traces");
-
-        testHitCountsBeforeStopping();
-
-        yield stopTracing(gPanel);
-
-        testHitCountsAfterStopping();
-
-        yield popPrefs();
-        yield closeDebuggerAndFinish(gPanel);
-      })();
-    });
-  })().catch(e => {
-    ok(false, "Got an error: " + e.message + "\n" + e.stack);
-  });
-}
-
-function clickButton() {
-  generateMouseClickInTab(gTab, "content.document.querySelector('button')");
-}
-
-function testHitCountsBeforeStopping() {
-  let marker = gEditor.getMarker(0, 'hit-counts');
-  ok(marker, "A counter should exists.");
-}
-
-function testHitCountsAfterStopping() {
-  let marker = gEditor.getMarker(0, 'hit-counts');
-  is(marker, undefined, "A counter should be cleared.");
-}
-
-registerCleanupFunction(function() {
-  gTab = null;
-  gPanel = null;
-  gDebugger = null;
-  gEditor = null;
-});
diff --git a/browser/devtools/debugger/test/browser_dbg_tracing-01.js b/browser/devtools/debugger/test/browser_dbg_tracing-01.js
deleted file mode 100644
index 272173c4d49..00000000000
--- a/browser/devtools/debugger/test/browser_dbg_tracing-01.js
+++ /dev/null
@@ -1,105 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-/**
- * Test that we get the expected frame enter/exit logs in the tracer view.
- */
-
-const TAB_URL = EXAMPLE_URL + "doc_tracing-01.html";
-
-let gTab, gPanel, gDebugger;
-
-function test() {
-  SpecialPowers.pushPrefEnv({'set': [["devtools.debugger.tracer", true]]}, () => {
-    initDebugger(TAB_URL).then(([aTab,, aPanel]) => {
-      gTab = aTab;
-      gPanel = aPanel;
-      gDebugger = gPanel.panelWin;
-
-      waitForSourceShown(gPanel, "code_tracing-01.js")
-        .then(() => startTracing(gPanel))
-        .then(clickButton)
-        .then(() => waitForClientEvents(aPanel, "traces"))
-        .then(testTraceLogs)
-        .then(() => stopTracing(gPanel))
-        .then(() => {
-          const deferred = promise.defer();
-          SpecialPowers.popPrefEnv(deferred.resolve);
-          return deferred.promise;
-        })
-        .then(() => closeDebuggerAndFinish(gPanel))
-        .then(null, aError => {
-          ok(false, "Got an error: " + aError.message + "\n" + aError.stack);
-        });
-    });
-  });
-}
-
-function clickButton() {
-  generateMouseClickInTab(gTab, "content.document.querySelector('button')");
-}
-
-function testTraceLogs() {
-  const onclickLogs = filterTraces(gPanel,
-                                   t => t.querySelector(".trace-name[value=onclick]"));
-  is(onclickLogs.length, 2, "Should have two logs from 'onclick'");
-  ok(onclickLogs[0].querySelector(".trace-call"),
-     "The first 'onclick' log should be a call.");
-  ok(onclickLogs[1].querySelector(".trace-return"),
-     "The second 'onclick' log should be a return.");
-  for (let t of onclickLogs) {
-    ok(t.querySelector(".trace-item").getAttribute("tooltiptext")
-        .includes("doc_tracing-01.html"));
-  }
-
-  const nonOnclickLogs = filterTraces(gPanel,
-                                      t => !t.querySelector(".trace-name[value=onclick]"));
-  for (let t of nonOnclickLogs) {
-    ok(t.querySelector(".trace-item").getAttribute("tooltiptext")
-        .includes("code_tracing-01.js"));
-  }
-
-  const mainLogs = filterTraces(gPanel,
-                                t => t.querySelector(".trace-name[value=main]"));
-  is(mainLogs.length, 2, "Should have an enter and an exit for 'main'");
-  ok(mainLogs[0].querySelector(".trace-call"),
-     "The first 'main' log should be a call.");
-  ok(mainLogs[1].querySelector(".trace-return"),
-     "The second 'main' log should be a return.");
-
-  const factorialLogs = filterTraces(gPanel,
-                                     t => t.querySelector(".trace-name[value=factorial]"));
-  is(factorialLogs.length, 10, "Should have 5 enter, and 5 exit frames for 'factorial'");
-  ok(factorialLogs.slice(0, 5).every(t => t.querySelector(".trace-call")),
-     "The first five 'factorial' logs should be calls.");
-  ok(factorialLogs.slice(5).every(t => t.querySelector(".trace-return")),
-     "The second five 'factorial' logs should be returns.")
-
-  // Test that the depth affects padding so that calls are indented properly.
-  let lastDepth = -Infinity;
-  for (let t of factorialLogs.slice(0, 5)) {
-    let depth = parseInt(t.querySelector(".trace-item").style.MozPaddingStart, 10);
-    ok(depth > lastDepth, "The depth should be increasing");
-    lastDepth = depth;
-  }
-  lastDepth = Infinity;
-  for (let t of factorialLogs.slice(5)) {
-    let depth = parseInt(t.querySelector(".trace-item").style.MozPaddingStart, 10);
-    ok(depth < lastDepth, "The depth should be decreasing");
-    lastDepth = depth;
-  }
-
-  const throwerLogs = filterTraces(gPanel,
-                                   t => t.querySelector(".trace-name[value=thrower]"));
-  is(throwerLogs.length, 2, "Should have an enter and an exit for 'thrower'");
-  ok(throwerLogs[0].querySelector(".trace-call"),
-     "The first 'thrower' log should be a call.");
-  ok(throwerLogs[1].querySelector(".trace-throw",
-     "The second 'thrower' log should be a throw."));
-}
-
-registerCleanupFunction(function() {
-  gTab = null;
-  gPanel = null;
-  gDebugger = null;
-});
diff --git a/browser/devtools/debugger/test/browser_dbg_tracing-02.js b/browser/devtools/debugger/test/browser_dbg_tracing-02.js
deleted file mode 100644
index 476aadbde81..00000000000
--- a/browser/devtools/debugger/test/browser_dbg_tracing-02.js
+++ /dev/null
@@ -1,74 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-/**
- * Test that we highlight matching calls and returns on hover.
- */
-
-const TAB_URL = EXAMPLE_URL + "doc_tracing-01.html";
-
-let gTab, gPanel, gDebugger;
-
-function test() {
-  SpecialPowers.pushPrefEnv({'set': [["devtools.debugger.tracer", true]]}, () => {
-    initDebugger(TAB_URL).then(([aTab,, aPanel]) => {
-      gTab = aTab;
-      gPanel = aPanel;
-      gDebugger = gPanel.panelWin;
-
-      waitForSourceShown(gPanel, "code_tracing-01.js")
-        .then(() => startTracing(gPanel))
-        .then(clickButton)
-        .then(() => waitForClientEvents(aPanel, "traces"))
-        .then(highlightCall)
-        .then(testReturnHighlighted)
-        .then(unhighlightCall)
-        .then(testNoneHighlighted)
-        .then(() => stopTracing(gPanel))
-        .then(() => {
-          const deferred = promise.defer();
-          SpecialPowers.popPrefEnv(deferred.resolve);
-          return deferred.promise;
-        })
-        .then(() => closeDebuggerAndFinish(gPanel))
-        .then(null, aError => {
-          ok(false, "Got an error: " + aError.message + "\n" + aError.stack);
-        });
-    });
-  });
-}
-
-function clickButton() {
-  generateMouseClickInTab(gTab, "content.document.querySelector('button')");
-}
-
-function highlightCall() {
-  const callTrace = filterTraces(gPanel, t => t.querySelector(".trace-name[value=main]"))[0];
-  EventUtils.sendMouseEvent({ type: "mouseover" },
-                            callTrace,
-                            gDebugger);
-}
-
-function testReturnHighlighted() {
-  const returnTrace = filterTraces(gPanel, t => t.querySelector(".trace-name[value=main]"))[1];
-  ok(Array.indexOf(returnTrace.querySelector(".trace-item").classList, "selected-matching") >= 0,
-     "The corresponding return log should be highlighted.");
-}
-
-function unhighlightCall() {
-  const callTrace = filterTraces(gPanel, t => t.querySelector(".trace-name[value=main]"))[0];
-  EventUtils.sendMouseEvent({ type: "mouseout" },
-                            callTrace,
-                            gDebugger);
-}
-
-function testNoneHighlighted() {
-  const highlightedTraces = filterTraces(gPanel, t => t.querySelector(".selected-matching"));
-  is(highlightedTraces.length, 0, "Shouldn't have any highlighted traces");
-}
-
-registerCleanupFunction(function() {
-  gTab = null;
-  gPanel = null;
-  gDebugger = null;
-});
diff --git a/browser/devtools/debugger/test/browser_dbg_tracing-03.js b/browser/devtools/debugger/test/browser_dbg_tracing-03.js
deleted file mode 100644
index 79c51068695..00000000000
--- a/browser/devtools/debugger/test/browser_dbg_tracing-03.js
+++ /dev/null
@@ -1,70 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-SimpleTest.requestCompleteLog();
-
-/**
- * Test that we can jump to function definitions by clicking on logs.
- */
-
-const TAB_URL = EXAMPLE_URL + "doc_tracing-01.html";
-
-let gTab, gPanel, gDebugger, gSources;
-
-function test() {
-  SpecialPowers.pushPrefEnv({'set': [["devtools.debugger.tracer", true]]}, () => {
-    initDebugger(TAB_URL).then(([aTab,, aPanel]) => {
-      gTab = aTab;
-      gPanel = aPanel;
-      gDebugger = gPanel.panelWin;
-      gSources = gDebugger.DebuggerView.Sources;
-
-      waitForSourceShown(gPanel, "code_tracing-01.js")
-        .then(() => startTracing(gPanel))
-        .then(() => clickButton())
-        .then(() => waitForClientEvents(aPanel, "traces"))
-        .then(() => {
-          // Switch away from the JS file so we can make sure that clicking on a
-          // log will switch us back to the correct JS file.
-          gSources.selectedValue = getSourceActor(gSources, TAB_URL);
-          return ensureSourceIs(aPanel, getSourceActor(gSources, TAB_URL), true);
-        })
-        .then(() => {
-          const finished = waitForSourceShown(gPanel, "code_tracing-01.js");
-          clickTraceLog();
-          return finished;
-        })
-        .then(testCorrectLine)
-        .then(() => stopTracing(gPanel))
-        .then(() => {
-          const deferred = promise.defer();
-          SpecialPowers.popPrefEnv(deferred.resolve);
-          return deferred.promise;
-        })
-        .then(() => closeDebuggerAndFinish(gPanel))
-        .then(null, aError => {
-          ok(false, "Got an error: " + aError.message + "\n" + aError.stack);
-        });
-    });
-  });
-}
-
-function clickButton() {
-  generateMouseClickInTab(gTab, "content.document.querySelector('button')");
-}
-
-function clickTraceLog() {
-  filterTraces(gPanel, t => t.querySelector(".trace-name[value=main]"))[0].click();
-}
-
-function testCorrectLine() {
-  is(gDebugger.DebuggerView.editor.getCursor().line, 18,
-     "The editor should have the function definition site's line selected.");
-}
-
-registerCleanupFunction(function() {
-  gTab = null;
-  gPanel = null;
-  gDebugger = null;
-  gSources = null;
-});
diff --git a/browser/devtools/debugger/test/browser_dbg_tracing-04.js b/browser/devtools/debugger/test/browser_dbg_tracing-04.js
deleted file mode 100644
index 9ec1c82210e..00000000000
--- a/browser/devtools/debugger/test/browser_dbg_tracing-04.js
+++ /dev/null
@@ -1,80 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-/**
- * Test that when we click on logs, we get the parameters/return value in the variables view.
- */
-
-const TAB_URL = EXAMPLE_URL + "doc_tracing-01.html";
-
-let gTab, gPanel, gDebugger;
-
-function test() {
-  SpecialPowers.pushPrefEnv({'set': [["devtools.debugger.tracer", true]]}, () => {
-    initDebugger(TAB_URL).then(([aTab,, aPanel]) => {
-      gTab = aTab;
-      gPanel = aPanel;
-      gDebugger = gPanel.panelWin;
-
-      waitForSourceShown(gPanel, "code_tracing-01.js")
-        .then(() => startTracing(gPanel))
-        .then(clickButton)
-        .then(() => waitForClientEvents(aPanel, "traces"))
-        .then(clickTraceCall)
-        .then(testParams)
-        .then(clickTraceReturn)
-        .then(testReturn)
-        .then(() => stopTracing(gPanel))
-        .then(() => {
-          const deferred = promise.defer();
-          SpecialPowers.popPrefEnv(deferred.resolve);
-          return deferred.promise;
-        })
-        .then(() => closeDebuggerAndFinish(gPanel))
-        .then(null, aError => {
-          DevToolsUtils.reportException("browser_dbg_tracing-04.js", aError);
-          ok(false, "Got an error: " + aError.message + "\n" + aError.stack);
-        });
-    });
-  });
-}
-
-function clickButton() {
-  generateMouseClickInTab(gTab, "content.document.querySelector('button')");
-}
-
-function clickTraceCall() {
-  filterTraces(gPanel, t => t.querySelector(".trace-name[value=factorial]"))[0]
-    .click();
-}
-
-function testParams() {
-  const name = gDebugger.document.querySelector(".variables-view-variable .name");
-  ok(name, "Should have a variable name");
-  is(name.getAttribute("value"), "n", "The variable name should be n");
-
-  const value = gDebugger.document.querySelector(".variables-view-variable .value.token-number");
-  ok(value, "Should have a variable value");
-  is(value.getAttribute("value"), "5", "The variable value should be 5");
-}
-
-function clickTraceReturn() {
-  filterTraces(gPanel, t => t.querySelector(".trace-name[value=factorial]"))
-    .pop().click();
-}
-
-function testReturn() {
-  const name = gDebugger.document.querySelector(".variables-view-variable .name");
-  ok(name, "Should have a variable name");
-  is(name.getAttribute("value"), "<return>", "The variable name should be <return>");
-
-  const value = gDebugger.document.querySelector(".variables-view-variable .value.token-number");
-  ok(value, "Should have a variable value");
-  is(value.getAttribute("value"), "120", "The variable value should be 120");
-}
-
-registerCleanupFunction(function() {
-  gTab = null;
-  gPanel = null;
-  gDebugger = null;
-});
diff --git a/browser/devtools/debugger/test/browser_dbg_tracing-05.js b/browser/devtools/debugger/test/browser_dbg_tracing-05.js
deleted file mode 100644
index c811618cb6a..00000000000
--- a/browser/devtools/debugger/test/browser_dbg_tracing-05.js
+++ /dev/null
@@ -1,81 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-/**
- * Test that text describing the tracing state is correctly displayed.
- */
-
-const TAB_URL = EXAMPLE_URL + "doc_tracing-01.html";
-
-let gTab, gPanel, gDebugger;
-let gTracer, gL10N;
-
-function test() {
-  SpecialPowers.pushPrefEnv({'set': [["devtools.debugger.tracer", true]]}, () => {
-    initDebugger(TAB_URL).then(([aTab,, aPanel]) => {
-      gTab = aTab;
-      gPanel = aPanel;
-      gDebugger = gPanel.panelWin;
-      gTracer = gDebugger.DebuggerView.Tracer;
-      gL10N = gDebugger.L10N;
-
-      waitForSourceShown(gPanel, "code_tracing-01.js")
-        .then(testTracingNotStartedText)
-        .then(() => gTracer._onStartTracing())
-        .then(testFunctionCallsUnavailableText)
-        .then(clickButton)
-        .then(() => waitForClientEvents(aPanel, "traces"))
-        .then(testNoEmptyText)
-        .then(() => gTracer._onClear())
-        .then(testFunctionCallsUnavailableText)
-        .then(() => gTracer._onStopTracing())
-        .then(testTracingNotStartedText)
-        .then(() => gTracer._onClear())
-        .then(testTracingNotStartedText)
-        .then(() => {
-          const deferred = promise.defer();
-          SpecialPowers.popPrefEnv(deferred.resolve);
-          return deferred.promise;
-        })
-        .then(() => closeDebuggerAndFinish(gPanel))
-        .then(null, aError => {
-          DevToolsUtils.reportException("browser_dbg_tracing-05.js", aError);
-          ok(false, "Got an error: " + aError.message + "\n" + aError.stack);
-        });
-    });
-  });
-}
-
-function testTracingNotStartedText() {
-  let label = gDebugger.document.querySelector("#tracer-tabpanel .fast-list-widget-empty-text");
-  ok(label,
-    "A label is displayed in the tracer tabpanel.");
-  is(label.getAttribute("value"), gL10N.getStr("tracingNotStartedText"),
-    "The correct {{tracingNotStartedText}} is displayed in the tracer tabpanel.");
-}
-
-function testFunctionCallsUnavailableText() {
-  let label = gDebugger.document.querySelector("#tracer-tabpanel .fast-list-widget-empty-text");
-  ok(label,
-    "A label is displayed in the tracer tabpanel.");
-  is(label.getAttribute("value"), gL10N.getStr("noFunctionCallsText"),
-    "The correct {{noFunctionCallsText}} is displayed in the tracer tabpanel.");
-}
-
-function testNoEmptyText() {
-  let label = gDebugger.document.querySelector("#tracer-tabpanel .fast-list-widget-empty-text");
-  ok(!label,
-    "No label should be displayed in the tracer tabpanel.");
-}
-
-function clickButton() {
-  generateMouseClickInTab(gTab, "content.document.querySelector('button')");
-}
-
-registerCleanupFunction(function() {
-  gTab = null;
-  gPanel = null;
-  gDebugger = null;
-  gTracer = null;
-  gL10N = null;
-});
diff --git a/browser/devtools/debugger/test/browser_dbg_tracing-06.js b/browser/devtools/debugger/test/browser_dbg_tracing-06.js
deleted file mode 100644
index f1f836ef38a..00000000000
--- a/browser/devtools/debugger/test/browser_dbg_tracing-06.js
+++ /dev/null
@@ -1,37 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-/**
- * Test that the tracer doesn't connect to the backend when tracing is disabled.
- */
-
-const TAB_URL = EXAMPLE_URL + "doc_tracing-01.html";
-const TRACER_PREF = "devtools.debugger.tracer";
-
-let gTab, gPanel, gDebugger;
-let gOriginalPref = Services.prefs.getBoolPref(TRACER_PREF);
-Services.prefs.setBoolPref(TRACER_PREF, false);
-
-function test() {
-  initDebugger(TAB_URL).then(([aTab,, aPanel]) => {
-    gTab = aTab;
-    gPanel = aPanel;
-    gDebugger = gPanel.panelWin;
-
-    waitForSourceShown(gPanel, "code_tracing-01.js")
-      .then(() => {
-        ok(!gDebugger.DebuggerController.traceClient, "Should not have a trace client");
-        closeDebuggerAndFinish(gPanel);
-      })
-      .then(null, aError => {
-        ok(false, "Got an error: " + aError.message + "\n" + aError.stack);
-      });
-  });
-}
-
-registerCleanupFunction(function() {
-  gTab = null;
-  gPanel = null;
-  gDebugger = null;
-  Services.prefs.setBoolPref(TRACER_PREF, gOriginalPref);
-});
diff --git a/browser/devtools/debugger/test/browser_dbg_tracing-07.js b/browser/devtools/debugger/test/browser_dbg_tracing-07.js
deleted file mode 100644
index dc1ccaec915..00000000000
--- a/browser/devtools/debugger/test/browser_dbg_tracing-07.js
+++ /dev/null
@@ -1,83 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-/**
- * Execute code both before and after blackboxing and test that we get
- * appropriately styled traces.
- */
-
-const TAB_URL = EXAMPLE_URL + "doc_tracing-01.html";
-
-let gTab, gPanel;
-
-function test() {
-  Task.async(function*() {
-    yield pushPref();
-
-    [gTab,, gPanel] = yield initDebugger(TAB_URL);
-
-    yield startTracing(gPanel);
-    yield clickButton();
-    yield waitForClientEvents(gPanel, "traces");
-
-    /**
-     * Test that there are some traces which are not blackboxed.
-     */
-    const firstBbButton = getBlackBoxButton(gPanel);
-    ok(!firstBbButton.checked, "Should not be black boxed by default");
-
-    const blackBoxedTraces =
-      gPanel.panelWin.document.querySelectorAll(".trace-item.black-boxed");
-    ok(blackBoxedTraces.length === 0, "There should no blackboxed traces.");
-
-    const notBlackBoxedTraces =
-      gPanel.panelWin.document.querySelectorAll(".trace-item:not(.black-boxed)");
-    ok(notBlackBoxedTraces.length > 0,
-      "There should be some traces which are not blackboxed.");
-
-    yield toggleBlackBoxing(gPanel);
-    yield clickButton();
-    yield waitForClientEvents(gPanel, "traces");
-
-    /**
-     * Test that there are some traces which are blackboxed.
-     */
-    const secondBbButton = getBlackBoxButton(gPanel);
-    ok(secondBbButton.checked, "The checkbox should no longer be checked.");
-    const traces =
-      gPanel.panelWin.document.querySelectorAll(".trace-item.black-boxed");
-    ok(traces.length > 0, "There should be some blackboxed traces.");
-
-    yield stopTracing(gPanel);
-    yield popPref();
-    yield closeDebuggerAndFinish(gPanel);
-
-    finish();
-  })().catch(e => {
-    ok(false, "Got an error: " + e.message + "\n" + e.stack);
-    finish();
-  });
-}
-
-function clickButton() {
-  generateMouseClickInTab(gTab, "content.document.querySelector('button')");
-}
-
-function pushPref() {
-  let deferred = promise.defer();
-  SpecialPowers.pushPrefEnv({'set': [["devtools.debugger.tracer", true]]},
-    deferred.resolve);
-  return deferred.promise;
-}
-
-function popPref() {
-  let deferred = promise.defer();
-  SpecialPowers.popPrefEnv(deferred.resolve);
-  return deferred.promise;
-}
-
-registerCleanupFunction(function() {
-  gTab = null;
-  gPanel = null;
-});
-
diff --git a/browser/devtools/debugger/test/browser_dbg_tracing-08.js b/browser/devtools/debugger/test/browser_dbg_tracing-08.js
deleted file mode 100644
index eb20ffa9fcc..00000000000
--- a/browser/devtools/debugger/test/browser_dbg_tracing-08.js
+++ /dev/null
@@ -1,59 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-/**
- * Test that tracing about:config doesn't produce errors.
- */
-
-const TAB_URL = "about:config";
-
-let gPanel, gDoneChecks;
-
-function test() {
-  gDoneChecks = promise.defer();
-  const tracerPref = promise.defer();
-  const configPref = promise.defer();
-  SpecialPowers.pushPrefEnv({'set': [["devtools.debugger.tracer", true]]}, tracerPref.resolve);
-  SpecialPowers.pushPrefEnv({'set': [["general.warnOnAboutConfig", false]]}, configPref.resolve);
-  promise.all([tracerPref.promise, configPref.promise]).then(() => {
-    initDebugger(TAB_URL).then(([,, aPanel]) => {
-      gPanel = aPanel;
-      gPanel.panelWin.gClient.addOneTimeListener("traces", testTraceLogs);
-    }).then(() => startTracing(gPanel))
-      .then(generateTrace)
-      .then(() => waitForClientEvents(gPanel, "traces"))
-      .then(() => gDoneChecks.promise)
-      .then(() => stopTracing(gPanel))
-      .then(resetPreferences)
-      .then(() => closeDebuggerAndFinish(gPanel))
-      .then(null, aError => {
-        ok(false, "Got an error: " + aError.message + "\n" + aError.stack);
-      });
-  });
-}
-
-function testTraceLogs(name, packet) {
-  info("Traces: " + packet.traces.length);
-  ok(packet.traces.length > 0, "Got some traces.");
-  ok(packet.traces.every(t => t.type != "enteredFrame" || !!t.location),
-     "All enteredFrame traces contain location.");
-  gDoneChecks.resolve();
-}
-
-function generateTrace(name, packet) {
-  // Interact with the page to cause JS execution.
-  let search = content.document.getElementById("textbox");
-  info("Interacting with the page.");
-  search.value = "devtools";
-}
-
-function resetPreferences() {
-  const deferred = promise.defer();
-  SpecialPowers.popPrefEnv(() => SpecialPowers.popPrefEnv(deferred.resolve));
-  return deferred.promise;
-}
-
-registerCleanupFunction(function() {
-  gPanel = null;
-  gDoneChecks = null;
-});
diff --git a/browser/devtools/debugger/test/code_tracing-01.js b/browser/devtools/debugger/test/code_tracing-01.js
deleted file mode 100644
index 81fc9a7c61e..00000000000
--- a/browser/devtools/debugger/test/code_tracing-01.js
+++ /dev/null
@@ -1,29 +0,0 @@
-function factorial(n) {
-  if (n <= 1) {
-    return 1;
-  } else {
-    return n * factorial(n - 1);
-  }
-}
-
-function* yielder(n) {
-  while (n-- >= 0) {
-    yield { value: n, squared: n * n };
-  }
-}
-
-function thrower() {
-  throw new Error("Curse your sudden but inevitable betrayal!");
-}
-
-function main() {
-  factorial(5);
-
-  // XXX bug 923729: Can't test yielding yet.
-  // for (let x of yielder(5)) {}
-
-  try {
-    thrower();
-  } catch (e) {
-  }
-}
diff --git a/browser/devtools/debugger/test/doc_same-line-functions.html b/browser/devtools/debugger/test/doc_same-line-functions.html
deleted file mode 100644
index dbdf2644d33..00000000000
--- a/browser/devtools/debugger/test/doc_same-line-functions.html
+++ /dev/null
@@ -1,15 +0,0 @@
-<!-- Any copyright is dedicated to the Public Domain.
-     http://creativecommons.org/publicdomain/zero/1.0/ -->
-<!doctype html>
-
-<html>
-  <head>
-    <meta charset="utf-8"/>
-    <title>Debugger Tracer test page</title>
-  </head>
-
-  <body>
-    <script src="code_same-line-functions.js"></script>
-    <button onclick="first()">Click me!</button>
-  </body>
-</html>
diff --git a/browser/devtools/debugger/test/doc_tracing-01.html b/browser/devtools/debugger/test/doc_tracing-01.html
deleted file mode 100644
index be3c7af1bdb..00000000000
--- a/browser/devtools/debugger/test/doc_tracing-01.html
+++ /dev/null
@@ -1,20 +0,0 @@
-<!DOCTYPE html>
-<html>
-  <head>
-    <meta charset="utf-8"/>
-    <title>Debugger Tracer test page</title>
-  </head>
-
-  <body>
-    <script src="code_tracing-01.js"></script>
-    <button onclick="main()">Click me!</button>
-
-    <script type="text/javascript">
-      // Have an inline script to make sure the HTML file is listed
-      // in the sources. We want to switch between them.
-      function foo() {
-        return 5;
-      }
-    </script>
-  </body>
-</html>
diff --git a/browser/devtools/debugger/test/head.js b/browser/devtools/debugger/test/head.js
index e872349520d..2188dc3cc85 100644
--- a/browser/devtools/debugger/test/head.js
+++ b/browser/devtools/debugger/test/head.js
@@ -888,39 +888,6 @@ function reopenVarPopup(...aArgs) {
   return hideVarPopup.apply(this, aArgs).then(() => openVarPopup.apply(this, aArgs));
 }
 
-// Tracing helpers
-
-function startTracing(aPanel) {
-  const deferred = promise.defer();
-  aPanel.panelWin.DebuggerController.Tracer.startTracing(aResponse => {
-    if (aResponse.error) {
-      deferred.reject(aResponse);
-    } else {
-      deferred.resolve(aResponse);
-    }
-  });
-  return deferred.promise;
-}
-
-function stopTracing(aPanel) {
-  const deferred = promise.defer();
-  aPanel.panelWin.DebuggerController.Tracer.stopTracing(aResponse => {
-    if (aResponse.error) {
-      deferred.reject(aResponse);
-    } else {
-      deferred.resolve(aResponse);
-    }
-  });
-  return deferred.promise;
-}
-
-function filterTraces(aPanel, f) {
-  const traces = aPanel.panelWin.document
-    .getElementById("tracer-traces")
-    .querySelector("scrollbox")
-    .children;
-  return Array.filter(traces, f);
-}
 function attachAddonActorForUrl(aClient, aUrl) {
   let deferred = promise.defer();
 
diff --git a/browser/devtools/debugger/views/tracer-view.js b/browser/devtools/debugger/views/tracer-view.js
deleted file mode 100644
index b3dbcbac845..00000000000
--- a/browser/devtools/debugger/views/tracer-view.js
+++ /dev/null
@@ -1,416 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-"use strict";
-
-/**
- * Functions handling the traces UI.
- */
-function TracerView(DebuggerController, DebuggerView) {
-  this._selectedItem = null;
-  this._matchingItems = null;
-  this.widget = null;
-
-  this.Tracer = DebuggerController.Tracer;
-  this.DebuggerView = DebuggerView;
-
-  this._highlightItem = this._highlightItem.bind(this);
-  this._isNotSelectedItem = this._isNotSelectedItem.bind(this);
-
-  this._unhighlightMatchingItems =
-    DevToolsUtils.makeInfallible(this._unhighlightMatchingItems.bind(this));
-  this._onToggleTracing =
-    DevToolsUtils.makeInfallible(this._onToggleTracing.bind(this));
-  this._onStartTracing =
-    DevToolsUtils.makeInfallible(this._onStartTracing.bind(this));
-  this._onClear =
-    DevToolsUtils.makeInfallible(this._onClear.bind(this));
-  this._onSelect =
-    DevToolsUtils.makeInfallible(this._onSelect.bind(this));
-  this._onMouseOver =
-    DevToolsUtils.makeInfallible(this._onMouseOver.bind(this));
-  this._onSearch =
-    DevToolsUtils.makeInfallible(this._onSearch.bind(this));
-}
-
-TracerView.MAX_TRACES = 200;
-
-TracerView.prototype = Heritage.extend(WidgetMethods, {
-  /**
-   * Initialization function, called when the debugger is started.
-   */
-  initialize: function() {
-    dumpn("Initializing the TracerView");
-
-    this._traceButton = document.getElementById("trace");
-    this._tracerTab = document.getElementById("tracer-tab");
-
-    // Remove tracer related elements from the dom and tear everything down if
-    // the tracer isn't enabled.
-    if (!Prefs.tracerEnabled) {
-      this._traceButton.remove();
-      this._traceButton = null;
-      this._tracerTab.remove();
-      this._tracerTab = null;
-      return;
-    }
-
-    this.widget = new FastListWidget(document.getElementById("tracer-traces"));
-    this._traceButton.removeAttribute("hidden");
-    this._tracerTab.removeAttribute("hidden");
-
-    this._search = document.getElementById("tracer-search");
-    this._template = document.getElementsByClassName("trace-item-template")[0];
-    this._templateItem = this._template.getElementsByClassName("trace-item")[0];
-    this._templateTypeIcon = this._template.getElementsByClassName("trace-type")[0];
-    this._templateNameNode = this._template.getElementsByClassName("trace-name")[0];
-
-    this.widget.addEventListener("select", this._onSelect, false);
-    this.widget.addEventListener("mouseover", this._onMouseOver, false);
-    this.widget.addEventListener("mouseout", this._unhighlightMatchingItems, false);
-    this._search.addEventListener("input", this._onSearch, false);
-
-    this._startTooltip = L10N.getStr("startTracingTooltip");
-    this._stopTooltip = L10N.getStr("stopTracingTooltip");
-    this._tracingNotStartedString = L10N.getStr("tracingNotStartedText");
-    this._noFunctionCallsString = L10N.getStr("noFunctionCallsText");
-
-    this._traceButton.setAttribute("tooltiptext", this._startTooltip);
-    this.emptyText = this._tracingNotStartedString;
-
-    this._addCommands();
-  },
-
-  /**
-   * Destruction function, called when the debugger is closed.
-   */
-  destroy: function() {
-    dumpn("Destroying the TracerView");
-
-    if (!this.widget) {
-      return;
-    }
-
-    this.widget.removeEventListener("select", this._onSelect, false);
-    this.widget.removeEventListener("mouseover", this._onMouseOver, false);
-    this.widget.removeEventListener("mouseout", this._unhighlightMatchingItems, false);
-    this._search.removeEventListener("input", this._onSearch, false);
-  },
-
-  /**
-   * Add commands that XUL can fire.
-   */
-  _addCommands: function() {
-    XULUtils.addCommands(document.getElementById('debuggerCommands'), {
-      toggleTracing: () => this._onToggleTracing(),
-      startTracing: () => this._onStartTracing(),
-      clearTraces: () => this._onClear()
-    });
-  },
-
-  /**
-   * Function invoked by the "toggleTracing" command to switch the tracer state.
-   */
-  _onToggleTracing: function() {
-    if (this.Tracer.tracing) {
-      this._onStopTracing();
-    } else {
-      this._onStartTracing();
-    }
-  },
-
-  /**
-   * Function invoked either by the "startTracing" command or by
-   * _onToggleTracing to start execution tracing in the backend.
-   *
-   * @return object
-   *         A promise resolved once the tracing has successfully started.
-   */
-  _onStartTracing: function() {
-    this._traceButton.setAttribute("checked", true);
-    this._traceButton.setAttribute("tooltiptext", this._stopTooltip);
-
-    this.empty();
-    this.emptyText = this._noFunctionCallsString;
-
-    let deferred = promise.defer();
-    this.Tracer.startTracing(deferred.resolve);
-    return deferred.promise;
-  },
-
-  /**
-   * Function invoked by _onToggleTracing to stop execution tracing in the
-   * backend.
-   *
-   * @return object
-   *         A promise resolved once the tracing has successfully stopped.
-   */
-  _onStopTracing: function() {
-    this._traceButton.removeAttribute("checked");
-    this._traceButton.setAttribute("tooltiptext", this._startTooltip);
-
-    this.emptyText = this._tracingNotStartedString;
-
-    let deferred = promise.defer();
-    this.Tracer.stopTracing(deferred.resolve);
-    return deferred.promise;
-  },
-
-  /**
-   * Function invoked by the "clearTraces" command to empty the traces pane.
-   */
-  _onClear: function() {
-    this.empty();
-  },
-
-  /**
-   * Populate the given parent scope with the variable with the provided name
-   * and value.
-   *
-   * @param String aName
-   *        The name of the variable.
-   * @param Object aParent
-   *        The parent scope.
-   * @param Object aValue
-   *        The value of the variable.
-   */
-  _populateVariable: function(aName, aParent, aValue) {
-    let item = aParent.addItem(aName, { value: aValue });
-
-    if (aValue) {
-      let wrappedValue = new this.Tracer.WrappedObject(aValue);
-      this.DebuggerView.Variables.controller.populate(item, wrappedValue);
-      item.expand();
-      item.twisty = false;
-    }
-  },
-
-  /**
-   * Handler for the widget's "select" event. Displays parameters, exception, or
-   * return value depending on whether the selected trace is a call, throw, or
-   * return respectively.
-   *
-   * @param Object traceItem
-   *        The selected trace item.
-   */
-  _onSelect: function _onSelect({ detail: traceItem }) {
-    if (!traceItem) {
-      return;
-    }
-
-    const data = traceItem.attachment.trace;
-    const { location: { url, line } } = data;
-    this.DebuggerView.setEditorLocation(
-      this.DebuggerView.Sources.getActorForLocation({ url }),
-      line,
-      { noDebug: true }
-    );
-
-    this.DebuggerView.Variables.empty();
-    const scope = this.DebuggerView.Variables.addScope();
-
-    if (data.type == "call") {
-      const params = DevToolsUtils.zip(data.parameterNames, data.arguments);
-      for (let [name, val] of params) {
-        if (val === undefined) {
-          scope.addItem(name, { value: "<value not available>" });
-        } else {
-          this._populateVariable(name, scope, val);
-        }
-      }
-    } else {
-      const varName = "<" + (data.type == "throw" ? "exception" : data.type) + ">";
-      this._populateVariable(varName, scope, data.returnVal);
-    }
-
-    scope.expand();
-    this.DebuggerView.showInstrumentsPane();
-  },
-
-  /**
-   * Add the hover frame enter/exit highlighting to a given item.
-   */
-  _highlightItem: function(aItem) {
-    if (!aItem || !aItem.target) {
-      return;
-    }
-    const trace = aItem.target.querySelector(".trace-item");
-    trace.classList.add("selected-matching");
-  },
-
-  /**
-   * Remove the hover frame enter/exit highlighting to a given item.
-   */
-  _unhighlightItem: function(aItem) {
-    if (!aItem || !aItem.target) {
-      return;
-    }
-    const match = aItem.target.querySelector(".selected-matching");
-    if (match) {
-      match.classList.remove("selected-matching");
-    }
-  },
-
-  /**
-   * Remove the frame enter/exit pair highlighting we do when hovering.
-   */
-  _unhighlightMatchingItems: function() {
-    if (this._matchingItems) {
-      this._matchingItems.forEach(this._unhighlightItem);
-      this._matchingItems = null;
-    }
-  },
-
-  /**
-   * Returns true if the given item is not the selected item.
-   */
-  _isNotSelectedItem: function(aItem) {
-    return aItem !== this.selectedItem;
-  },
-
-  /**
-   * Highlight the frame enter/exit pair of items for the given item.
-   */
-  _highlightMatchingItems: function(aItem) {
-    const frameId = aItem.attachment.trace.frameId;
-    const predicate = e => e.attachment.trace.frameId == frameId;
-
-    this._unhighlightMatchingItems();
-    this._matchingItems = this.items.filter(predicate);
-    this._matchingItems
-      .filter(this._isNotSelectedItem)
-      .forEach(this._highlightItem);
-  },
-
-  /**
-   * Listener for the mouseover event.
-   */
-  _onMouseOver: function({ target }) {
-    const traceItem = this.getItemForElement(target);
-    if (traceItem) {
-      this._highlightMatchingItems(traceItem);
-    }
-  },
-
-  /**
-   * Listener for typing in the search box.
-   */
-  _onSearch: function() {
-    const query = this._search.value.trim().toLowerCase();
-    const predicate = name => name.toLowerCase().includes(query);
-    this.filterContents(item => predicate(item.attachment.trace.name));
-  },
-
-  /**
-   * Select the traces tab in the sidebar.
-   */
-  selectTab: function() {
-    const tabs = this._tracerTab.parentElement;
-    tabs.selectedIndex = Array.indexOf(tabs.children, this._tracerTab);
-  },
-
-  /**
-   * Commit all staged items to the widget. Overridden so that we can call
-   * |FastListWidget.prototype.flush|.
-   */
-  commit: function() {
-    WidgetMethods.commit.call(this);
-    // TODO: Accessing non-standard widget properties. Figure out what's the
-    // best way to expose such things. Bug 895514.
-    this.widget.flush();
-  },
-
-  /**
-   * Adds the trace record provided as an argument to the view.
-   *
-   * @param object aTrace
-   *        The trace record coming from the tracer actor.
-   */
-  addTrace: function(aTrace) {
-    // Create the element node for the trace item.
-    let view = this._createView(aTrace);
-
-    // Append a source item to this container.
-    this.push([view], {
-      staged: true,
-      attachment: {
-        trace: aTrace
-      }
-    });
-  },
-
-  /**
-   * Customization function for creating an item's UI.
-   *
-   * @return nsIDOMNode
-   *         The network request view.
-   */
-  _createView: function(aTrace) {
-    let { type, name, location, blackBoxed, depth, frameId } = aTrace;
-    let { parameterNames, returnVal, arguments: args } = aTrace;
-    let fragment = document.createDocumentFragment();
-
-    this._templateItem.classList.toggle("black-boxed", blackBoxed);
-    this._templateItem.setAttribute("tooltiptext", SourceUtils.trimUrl(location.url));
-    this._templateItem.style.MozPaddingStart = depth + "em";
-
-    const TYPES = ["call", "yield", "return", "throw"];
-    for (let t of TYPES) {
-      this._templateTypeIcon.classList.toggle("trace-" + t, t == type);
-    }
-    this._templateTypeIcon.setAttribute("value", {
-      call: "\u2192",
-      yield: "Y",
-      return: "\u2190",
-      throw: "E",
-      terminated: "TERMINATED"
-    }[type]);
-
-    this._templateNameNode.setAttribute("value", name);
-
-    // All extra syntax and parameter nodes added.
-    const addedNodes = [];
-
-    if (parameterNames) {
-      const syntax = (p) => {
-        const el = document.createElement("label");
-        el.setAttribute("value", p);
-        el.classList.add("trace-syntax");
-        el.classList.add("plain");
-        addedNodes.push(el);
-        return el;
-      };
-
-      this._templateItem.appendChild(syntax("("));
-
-      for (let i = 0, n = parameterNames.length; i < n; i++) {
-        let param = document.createElement("label");
-        param.setAttribute("value", parameterNames[i]);
-        param.classList.add("trace-param");
-        param.classList.add("plain");
-        addedNodes.push(param);
-        this._templateItem.appendChild(param);
-
-        if (i + 1 !== n) {
-          this._templateItem.appendChild(syntax(", "));
-        }
-      }
-
-      this._templateItem.appendChild(syntax(")"));
-    }
-
-    // Flatten the DOM by removing one redundant box (the template container).
-    for (let node of this._template.childNodes) {
-      fragment.appendChild(node.cloneNode(true));
-    }
-
-    // Remove any added nodes from the template.
-    for (let node of addedNodes) {
-      this._templateItem.removeChild(node);
-    }
-
-    return fragment;
-  }
-});
-
-DebuggerView.Tracer = new TracerView(DebuggerController, DebuggerView);
diff --git a/browser/devtools/jar.mn b/browser/devtools/jar.mn
index ddee64ab2e0..99a3f3cbbb0 100644
--- a/browser/devtools/jar.mn
+++ b/browser/devtools/jar.mn
@@ -71,7 +71,6 @@ browser.jar:
     content/browser/devtools/debugger/workers-view.js                  (debugger/views/workers-view.js)
     content/browser/devtools/debugger/sources-view.js                  (debugger/views/sources-view.js)
     content/browser/devtools/debugger/variable-bubble-view.js          (debugger/views/variable-bubble-view.js)
-    content/browser/devtools/debugger/tracer-view.js                   (debugger/views/tracer-view.js)
     content/browser/devtools/debugger/watch-expressions-view.js        (debugger/views/watch-expressions-view.js)
     content/browser/devtools/debugger/event-listeners-view.js          (debugger/views/event-listeners-view.js)
     content/browser/devtools/debugger/global-search-view.js            (debugger/views/global-search-view.js)