--- a/browser/devtools/scratchpad/test/browser_scratchpad_wrong_window_focus.js
+++ b/browser/devtools/scratchpad/test/browser_scratchpad_wrong_window_focus.js
@@ -43,17 +43,17 @@ function test()
 }
 
 function testFocus(sw, hud) {
   let sp = sw.Scratchpad;
 
   function onMessage(event, messages) {
     let msg = [...messages][0];
 
-    var loc = msg.querySelector(".location");
+    var loc = msg.querySelector(".message-location");
     ok(loc, "location element exists");
     is(loc.textContent.trim(), sw.Scratchpad.uniqueName + ":1",
         "location value is correct");
 
     sw.addEventListener("focus", function onFocus() {
       sw.removeEventListener("focus", onFocus, true);
 
       let win = Services.wm.getMostRecentWindow("devtools:scratchpad");

--- a/browser/devtools/webconsole/console-output.js
+++ b/browser/devtools/webconsole/console-output.js
@@ -141,16 +141,28 @@ ConsoleOutput.prototype = {
    * Getter for the debugger WebConsoleClient.
    * @type object
    */
   get webConsoleClient() {
     return this.owner.webConsoleClient;
   },
 
   /**
+   * Release an actor.
+   *
+   * @private
+   * @param string actorId
+   *        The actor ID you want to release.
+   */
+  _releaseObject: function(actorId)
+  {
+    this.owner._releaseObject(actorId);
+  },
+
+  /**
    * Add a message to output.
    *
    * @param object ...args
    *        Any number of Message objects.
    * @return this
    */
   addMessage: function(...args)
   {
@@ -842,17 +854,17 @@ Messages.Simple.prototype = Heritage.ext
   _renderRepeatNode: function()
   {
     if (!this._filterDuplicates) {
       return null;
     }
 
     let repeatNode = this.document.createElementNS(XHTML_NS, "span");
     repeatNode.setAttribute("value", "1");
-    repeatNode.className = "repeats";
+    repeatNode.className = "message-repeats";
     repeatNode.textContent = 1;
     repeatNode._uid = this.getRepeatID();
     return repeatNode;
   },
 
   /**
    * Render the message source location DOM element.
    * @private
@@ -1072,16 +1084,144 @@ Messages.ConsoleGeneric = function(packe
 Messages.ConsoleGeneric.prototype = Heritage.extend(Messages.Extended.prototype,
 {
   _renderBodyPieceSeparator: function()
   {
     return this.document.createTextNode(" ");
   },
 }); // Messages.ConsoleGeneric.prototype
 
+/**
+ * The ConsoleTrace message is used for console.trace() calls.
+ *
+ * @constructor
+ * @extends Messages.Simple
+ * @param object packet
+ *        The Console API call packet received from the server.
+ */
+Messages.ConsoleTrace = function(packet)
+{
+  let options = {
+    className: "consoleTrace cm-s-mozilla",
+    timestamp: packet.timeStamp,
+    category: "webdev",
+    severity: CONSOLE_API_LEVELS_TO_SEVERITIES[packet.level],
+    private: packet.private,
+    filterDuplicates: true,
+    location: {
+      url: packet.filename,
+      line: packet.lineNumber,
+    },
+  };
+
+  this._renderStack = this._renderStack.bind(this);
+  Messages.Simple.call(this, this._renderStack, options);
+
+  this._repeatID.consoleApiLevel = packet.level;
+  this._stacktrace = this._repeatID.stacktrace = packet.stacktrace;
+  this._arguments = packet.arguments;
+};
+
+Messages.ConsoleTrace.prototype = Heritage.extend(Messages.Simple.prototype,
+{
+  /**
+   * Holds the stackframes received from the server.
+   *
+   * @private
+   * @type array
+   */
+  _stacktrace: null,
+
+  /**
+   * Holds the arguments the content script passed to the console.trace()
+   * method. This array is cleared when the message is initialized, and
+   * associated actors are released.
+   *
+   * @private
+   * @type array
+   */
+  _arguments: null,
+
+  init: function()
+  {
+    let result = Messages.Simple.prototype.init.apply(this, arguments);
+
+    // We ignore console.trace() arguments. Release object actors.
+    if (Array.isArray(this._arguments)) {
+      for (let arg of this._arguments) {
+        if (WebConsoleUtils.isActorGrip(arg)) {
+          this.output._releaseObject(arg.actor);
+        }
+      }
+    }
+    this._arguments = null;
+
+    return result;
+  },
+
+  /**
+   * Render the stack frames.
+   *
+   * @private
+   * @return DOMElement
+   */
+  _renderStack: function()
+  {
+    let cmvar = this.document.createElementNS(XHTML_NS, "span");
+    cmvar.className = "cm-variable";
+    cmvar.textContent = "console";
+
+    let cmprop = this.document.createElementNS(XHTML_NS, "span");
+    cmprop.className = "cm-property";
+    cmprop.textContent = "trace";
+
+    let title = this.document.createElementNS(XHTML_NS, "span");
+    title.className = "title devtools-monospace";
+    title.appendChild(cmvar);
+    title.appendChild(this.document.createTextNode("."));
+    title.appendChild(cmprop);
+    title.appendChild(this.document.createTextNode("():"));
+
+    let repeatNode = Messages.Simple.prototype._renderRepeatNode.call(this);
+    let location = Messages.Simple.prototype._renderLocation.call(this);
+    if (location) {
+      location.target = "jsdebugger";
+    }
+
+    let widget = new Widgets.Stacktrace(this, this._stacktrace).render();
+
+    let body = this.document.createElementNS(XHTML_NS, "div");
+    body.appendChild(title);
+    if (repeatNode) {
+      body.appendChild(repeatNode);
+    }
+    if (location) {
+      body.appendChild(location);
+    }
+    body.appendChild(this.document.createTextNode("\n"));
+
+    let frag = this.document.createDocumentFragment();
+    frag.appendChild(body);
+    frag.appendChild(widget.element);
+
+    return frag;
+  },
+
+  _renderBody: function()
+  {
+    let body = Messages.Simple.prototype._renderBody.apply(this, arguments);
+    body.classList.remove("devtools-monospace");
+    return body;
+  },
+
+  // no-op for the message location and .repeats elements.
+  // |this._renderStack| handles customized message output.
+  _renderLocation: function() { },
+  _renderRepeatNode: function() { },
+}); // Messages.ConsoleTrace.prototype
 
 let Widgets = {};
 
 /**
  * The base widget class.
  *
  * @constructor
  * @param object message
@@ -1349,16 +1489,101 @@ Widgets.LongString.prototype = Heritage.
       category: "output",
       severity: "warning",
     });
     this.output.addMessage(msg);
   },
 }); // Widgets.LongString.prototype
 
 
+/**
+ * The stacktrace widget.
+ *
+ * @constructor
+ * @extends Widgets.BaseWidget
+ * @param object message
+ *        The owning message.
+ * @param array stacktrace
+ *        The stacktrace to display, array of frames as supplied by the server,
+ *        over the remote protocol.
+ */
+Widgets.Stacktrace = function(message, stacktrace)
+{
+  Widgets.BaseWidget.call(this, message);
+  this.stacktrace = stacktrace;
+};
+
+Widgets.Stacktrace.prototype = Heritage.extend(Widgets.BaseWidget.prototype,
+{
+  /**
+   * The stackframes received from the server.
+   * @type array
+   */
+  stacktrace: null,
+
+  render: function()
+  {
+    if (this.element) {
+      return this;
+    }
+
+    let result = this.element = this.document.createElementNS(XHTML_NS, "ul");
+    result.className = "stacktrace devtools-monospace";
+
+    for (let frame of this.stacktrace) {
+      result.appendChild(this._renderFrame(frame));
+    }
+
+    return this;
+  },
+
+  /**
+   * Render a frame object received from the server.
+   *
+   * @param object frame
+   *        The stack frame to display. This object should have the following
+   *        properties: functionName, filename and lineNumber.
+   * @return DOMElement
+   *         The DOM element to display for the given frame.
+   */
+  _renderFrame: function(frame)
+  {
+    let fn = this.document.createElementNS(XHTML_NS, "span");
+    fn.className = "function";
+    if (frame.functionName) {
+      let span = this.document.createElementNS(XHTML_NS, "span");
+      span.className = "cm-variable";
+      span.textContent = frame.functionName;
+      fn.appendChild(span);
+      fn.appendChild(this.document.createTextNode("()"));
+    } else {
+      fn.classList.add("cm-comment");
+      fn.textContent = l10n.getStr("stacktrace.anonymousFunction");
+    }
+
+    let location = this.output.owner.createLocationNode(frame.filename,
+                                                        frame.lineNumber,
+                                                        "jsdebugger");
+
+    // .devtools-monospace sets font-size to 80%, however .body already has
+    // .devtools-monospace. If we keep it here, the location would be rendered
+    // smaller.
+    location.classList.remove("devtools-monospace");
+
+    let elem = this.document.createElementNS(XHTML_NS, "li");
+    elem.appendChild(fn);
+    elem.appendChild(location);
+    elem.appendChild(this.document.createTextNode("\n"));
+
+    return elem;
+  },
+
+}); // Widgets.Stacktrace.prototype
+
+
 function gSequenceId()
 {
   return gSequenceId.n++;
 }
 gSequenceId.n = 0;
 
 exports.ConsoleOutput = ConsoleOutput;
 exports.Messages = Messages;

--- a/browser/devtools/webconsole/test/browser.ini
+++ b/browser/devtools/webconsole/test/browser.ini
@@ -98,16 +98,17 @@ support-files =
   test_bug_770099_bad_policy_uri.html^headers^
   test_bug_770099_violation.html
   test_bug_770099_violation.html^headers^
   test-autocomplete-in-stackframe.html
   testscript.js
   test-bug_923281_console_log_filter.html
   test-bug_923281_test1.js
   test-bug_923281_test2.js
+  test-bug_939783_console_trace_duplicates.html
 
 [browser_bug664688_sandbox_update_after_navigation.js]
 [browser_bug_638949_copy_link_location.js]
 [browser_bug_862916_console_dir_and_filter_off.js]
 [browser_bug_865288_repeat_different_objects.js]
 [browser_bug_865871_variables_view_close_on_esc_key.js]
 [browser_bug_869003_inspect_cross_domain_object.js]
 [browser_bug_871156_ctrlw_close_tab.js]
@@ -252,8 +253,9 @@ run-if = os == "mac"
 [browser_webconsole_expandable_timestamps.js]
 [browser_webconsole_autocomplete_in_debugger_stackframe.js]
 [browser_webconsole_autocomplete_popup_close_on_tab_switch.js]
 [browser_webconsole_output_01.js]
 [browser_webconsole_output_02.js]
 [browser_webconsole_output_03.js]
 [browser_webconsole_output_04.js]
 [browser_webconsole_output_events.js]
+[browser_webconsole_console_trace_duplicates.js]

--- a/browser/devtools/webconsole/test/browser_console_addonsdk_loader_exception.js
+++ b/browser/devtools/webconsole/test/browser_console_addonsdk_loader_exception.js
@@ -65,17 +65,17 @@ function test()
       onMessageFound(results);
     });
   }
 
   function onMessageFound(results)
   {
     let msg = [...results[0].matched][0];
     ok(msg, "message element found");
-    let locationNode = msg.querySelector(".location");
+    let locationNode = msg.querySelector(".message-location");
     ok(locationNode, "message location element found");
 
     let title = locationNode.getAttribute("title");
     info("location node title: " + title);
     isnot(title.indexOf(" -> "), -1, "error comes from a subscript");
 
     let viewSource = browserconsole.viewSource;
     let URL = null;

--- a/browser/devtools/webconsole/test/browser_console_error_source_click.js
+++ b/browser/devtools/webconsole/test/browser_console_error_source_click.js
@@ -56,17 +56,17 @@ function test()
     let viewSourceCalled = false;
     hud.viewSource = () => viewSourceCalled = true;
 
     for (let result of results) {
       viewSourceCalled = false;
 
       let msg = [...results[0].matched][0];
       ok(msg, "message element found for: " + result.text);
-      let locationNode = msg.querySelector(".location");
+      let locationNode = msg.querySelector(".message-location");
       ok(locationNode, "message location element found");
 
       EventUtils.synthesizeMouse(locationNode, 2, 2, {}, hud.iframeWindow);
 
       ok(viewSourceCalled, "view source opened");
     }
 
     hud.viewSource = viewSource;

--- a/browser/devtools/webconsole/test/browser_webconsole_bug_585956_console_trace.js
+++ b/browser/devtools/webconsole/test/browser_webconsole_bug_585956_console_trace.js
@@ -1,49 +1,46 @@
 /* vim:set ts=2 sw=2 sts=2 et: */
 /* 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/. */
 
 const TEST_URI = "http://example.com/browser/browser/devtools/webconsole/test/test-bug-585956-console-trace.html";
 
 function test() {
-  addTab("data:text/html;charset=utf8,<p>hello");
-  browser.addEventListener("load", tabLoaded, true);
+  Task.spawn(runner).then(finishTest);
 
-  function tabLoaded() {
-    browser.removeEventListener("load", tabLoaded, true);
+  function* runner() {
+    let {tab} = yield loadTab("data:text/html;charset=utf8,<p>hello");
+    let hud = yield openConsole(tab);
 
-    openConsole(null, function(hud) {
-      content.location = TEST_URI;
+    content.location = TEST_URI;
 
-      waitForMessages({
-        webconsole: hud,
-        messages: [{
-          name: "console.trace output",
-          consoleTrace: {
-            file: "test-bug-585956-console-trace.html",
-            fn: "window.foobar585956c",
-          },
-        }],
-      }).then(performChecks);
+    let [result] = yield waitForMessages({
+      webconsole: hud,
+      messages: [{
+        name: "console.trace output",
+        consoleTrace: {
+          file: "test-bug-585956-console-trace.html",
+          fn: "window.foobar585956c",
+        },
+      }],
     });
-  }
 
-  function performChecks(results) {
-    let node = [...results[0].matched][0];
+    let node = [...result.matched][0];
+    ok(node, "found trace log node");
+
+    let obj = node._messageObject;
+    ok(obj, "console.trace message object");
 
     // The expected stack trace object.
     let stacktrace = [
       { filename: TEST_URI, lineNumber: 9, functionName: "window.foobar585956c", language: 2 },
       { filename: TEST_URI, lineNumber: 14, functionName: "foobar585956b", language: 2 },
       { filename: TEST_URI, lineNumber: 18, functionName: "foobar585956a", language: 2 },
       { filename: TEST_URI, lineNumber: 21, functionName: null, language: 2 }
     ];
 
-    ok(node, "found trace log node");
-    ok(node._stacktrace, "found stacktrace object");
-    is(node._stacktrace.toSource(), stacktrace.toSource(), "stacktrace is correct");
+    ok(obj._stacktrace, "found stacktrace object");
+    is(obj._stacktrace.toSource(), stacktrace.toSource(), "stacktrace is correct");
     isnot(node.textContent.indexOf("bug-585956"), -1, "found file name");
-
-    finishTest();
   }
 }

--- a/browser/devtools/webconsole/test/browser_webconsole_bug_642108_pruneTest.js
+++ b/browser/devtools/webconsole/test/browser_webconsole_bug_642108_pruneTest.js
@@ -69,17 +69,17 @@ function testCSSPruning(hudRef) {
       }],
     }).then(([result]) => {
       is(countMessageNodes(), LOG_LIMIT, "number of messages");
 
       is(Object.keys(hudRef.ui._repeatNodes).length, LOG_LIMIT,
          "repeated nodes pruned from repeatNodes");
 
       let msg = [...result.matched][0];
-      let repeats = msg.querySelector(".repeats");
+      let repeats = msg.querySelector(".message-repeats");
       is(repeats.getAttribute("value"), 1,
          "repeated nodes pruned from repeatNodes (confirmed)");
 
       finishTest();
     });
   });
 }
 

--- a/browser/devtools/webconsole/test/browser_webconsole_bug_766001_JS_Console_in_Debugger.js
+++ b/browser/devtools/webconsole/test/browser_webconsole_bug_766001_JS_Console_in_Debugger.js
@@ -29,18 +29,18 @@ function test() {
         text: "Blah Blah",
         category: CATEGORY_WEBDEV,
         severity: SEVERITY_LOG,
       }],
     });
 
     let exceptionMsg = [...exceptionRule.matched][0];
     let consoleMsg = [...consoleRule.matched][0];
-    let nodes = [exceptionMsg.querySelector(".location"),
-                 consoleMsg.querySelector(".location")];
+    let nodes = [exceptionMsg.querySelector(".message-location"),
+                 consoleMsg.querySelector(".message-location")];
     ok(nodes[0], ".location node for the exception message");
     ok(nodes[1], ".location node for the console message");
 
     for (let i = 0; i < nodes.length; i++) {
       yield checkClickOnNode(i, nodes[i]);
       yield gDevTools.showToolbox(hud.target, "webconsole");
     }
 

--- a/browser/devtools/webconsole/test/browser_webconsole_bug_782653_CSS_links_in_Style_Editor.js
+++ b/browser/devtools/webconsole/test/browser_webconsole_bug_782653_CSS_links_in_Style_Editor.js
@@ -36,20 +36,20 @@ function testViewSource(aHud)
     {
       text: "'color'",
       category: CATEGORY_CSS,
       severity: SEVERITY_WARNING,
     }],
   }).then(([error1Rule, error2Rule]) => {
     let error1Msg = [...error1Rule.matched][0];
     let error2Msg = [...error2Rule.matched][0];
-    nodes = [error1Msg.querySelector(".location"),
-             error2Msg.querySelector(".location")];
-    ok(nodes[0], ".location node for the first error");
-    ok(nodes[1], ".location node for the second error");
+    nodes = [error1Msg.querySelector(".message-location"),
+             error2Msg.querySelector(".message-location")];
+    ok(nodes[0], ".message-location node for the first error");
+    ok(nodes[1], ".message-location node for the second error");
 
     let target = TargetFactory.forTab(gBrowser.selectedTab);
     let toolbox = gDevTools.getToolbox(target);
     toolbox.once("styleeditor-selected", (event, panel) => {
       StyleEditorUI = panel.UI;
 
       let count = 0;
       StyleEditorUI.on("editor-added", function() {

new file mode 100644
--- /dev/null
+++ b/browser/devtools/webconsole/test/browser_webconsole_console_trace_duplicates.js
@@ -0,0 +1,36 @@
+/* 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/. */
+
+function test() {
+  const TEST_URI = "http://example.com/browser/browser/devtools/webconsole/test/test-bug_939783_console_trace_duplicates.html";
+
+  Task.spawn(runner).then(finishTest);
+
+  function* runner() {
+    const {tab} = yield loadTab("data:text/html;charset=utf8,<p>hello");
+    const hud = yield openConsole(tab);
+
+    content.location = TEST_URI;
+
+    yield waitForMessages({
+      webconsole: hud,
+      messages: [{
+        name: "console.trace output for foo1()",
+        text: "foo1()",
+        repeats: 2,
+        consoleTrace: {
+          file: "test-bug_939783_console_trace_duplicates.html",
+          fn: "foo3()",
+        },
+      }, {
+        name: "console.trace output for foo1b()",
+        text: "foo1b()",
+        consoleTrace: {
+          file: "test-bug_939783_console_trace_duplicates.html",
+          fn: "foo3()",
+        },
+      }],
+    });
+  }
+}

--- a/browser/devtools/webconsole/test/browser_webconsole_scratchpad_panel_link.js
+++ b/browser/devtools/webconsole/test/browser_webconsole_scratchpad_panel_link.js
@@ -48,17 +48,17 @@ function runTests(aToolbox)
       webconsole: hud,
       messages: [{ text: "foobar-from-scratchpad" }]
     });
 
     info("Clicking link to switch to and focus Scratchpad");
 
     let [matched] = [...messages[0].matched];
     ok(matched, "Found logged message from Scratchpad");
-    let anchor = matched.querySelector("a.location");
+    let anchor = matched.querySelector("a.message-location");
 
     aToolbox.on("scratchpad-selected", function selected() {
       aToolbox.off("scratchpad-selected", selected);
 
       is(aToolbox.getCurrentPanel(), scratchpadPanel,
         "Clicking link switches to Scratchpad panel");
       
       is(Services.ww.activeWindow, aToolbox.frame.ownerGlobal,

--- a/browser/devtools/webconsole/test/browser_webconsole_view_source.js
+++ b/browser/devtools/webconsole/test/browser_webconsole_view_source.js
@@ -42,17 +42,17 @@ function testViewSource(hud) {
         }],
       }).then(onMessage);
     });
   });
 
   function onMessage([result]) {
     let msg = [...result.matched][0];
     ok(msg, "error message");
-    let locationNode = msg.querySelector(".location");
+    let locationNode = msg.querySelector(".message-location");
     ok(locationNode, "location node");
 
     Services.ww.registerNotification(observer);
 
     containsValue = Sources.containsValue;
     Sources.containsValue = () => {
       containsValueInvoked = true;
       return false;

--- a/browser/devtools/webconsole/test/head.js
+++ b/browser/devtools/webconsole/test/head.js
@@ -1,26 +1,22 @@
 /* vim:set ts=2 sw=2 sts=2 et: */
 /* 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/. */
 
-let WebConsoleUtils, TargetFactory, require;
 let {gDevTools} = Cu.import("resource:///modules/devtools/gDevTools.jsm", {});
 let {console} = Cu.import("resource://gre/modules/devtools/Console.jsm", {});
 let {Promise: promise} = Cu.import("resource://gre/modules/commonjs/sdk/core/promise.js", {});
 let {Task} = Cu.import("resource://gre/modules/Task.jsm", {});
+let {devtools} = Cu.import("resource://gre/modules/devtools/Loader.jsm", {});
+let {require, TargetFactory} = devtools;
+let {Utils: WebConsoleUtils} = require("devtools/toolkit/webconsole/utils");
+let {Messages} = require("devtools/webconsole/console-output");
 
-(() => {
-  let {devtools} = Cu.import("resource://gre/modules/devtools/Loader.jsm", {});
-  let utils = devtools.require("devtools/toolkit/webconsole/utils");
-  TargetFactory = devtools.TargetFactory;
-  WebConsoleUtils = utils.Utils;
-  require = devtools.require;
-})();
 // promise._reportErrors = true; // please never leave me.
 
 let gPendingOutputTest = 0;
 
 // The various categories of messages.
 const CATEGORY_NETWORK = 0;
 const CATEGORY_CSS = 1;
 const CATEGORY_JS = 2;
@@ -278,17 +274,17 @@ function dumpConsoles()
  * Dump to output debug information for the given webconsole message.
  *
  * @param nsIDOMNode aMessage
  *        The message element you want to display.
  */
 function dumpMessageElement(aMessage)
 {
   let text = aMessage.textContent;
-  let repeats = aMessage.querySelector(".repeats");
+  let repeats = aMessage.querySelector(".message-repeats");
   if (repeats) {
     repeats = repeats.getAttribute("value");
   }
   console.debug("id", aMessage.getAttribute("id"),
                 "date", aMessage.timestamp,
                 "class", aMessage.className,
                 "category", aMessage.category,
                 "severity", aMessage.severity,
@@ -927,54 +923,54 @@ function waitForMessages(aOptions)
     return result;
   }
 
   function checkConsoleTrace(aRule, aElement)
   {
     let elemText = aElement.textContent;
     let trace = aRule.consoleTrace;
 
-    if (!checkText("Stack trace from ", elemText)) {
+    if (!checkText("console.trace():", elemText)) {
       return false;
     }
 
-    let clickable = aElement.querySelector(".body a");
-    if (!clickable) {
-      ok(false, "console.trace() message is missing .hud-clickable");
-      displayErrorContext(aRule, aElement);
-      return false;
-    }
-    aRule.clickableElements = [clickable];
-
-    if (trace.file &&
-        !checkText("from " + trace.file + ", ", elemText)) {
-      ok(false, "console.trace() message is missing the file name: " +
-                trace.file);
-      displayErrorContext(aRule, aElement);
-      return false;
+    let frame = aElement.querySelector(".stacktrace li:first-child");
+    if (trace.file) {
+      let file = frame.querySelector(".message-location").title;
+      if (!checkText(trace.file, file)) {
+        ok(false, "console.trace() message is missing the file name: " +
+                  trace.file);
+        displayErrorContext(aRule, aElement);
+        return false;
+      }
     }
 
-    if (trace.fn &&
-        !checkText(", function " + trace.fn + ", ", elemText)) {
-      ok(false, "console.trace() message is missing the function name: " +
-                trace.fn);
-      displayErrorContext(aRule, aElement);
-      return false;
+    if (trace.fn) {
+      let fn = frame.querySelector(".function").textContent;
+      if (!checkText(trace.fn, fn)) {
+        ok(false, "console.trace() message is missing the function name: " +
+                  trace.fn);
+        displayErrorContext(aRule, aElement);
+        return false;
+      }
     }
 
-    if (trace.line &&
-        !checkText(", line " + trace.line + ".", elemText)) {
-      ok(false, "console.trace() message is missing the line number: " +
-                trace.line);
-      displayErrorContext(aRule, aElement);
-      return false;
+    if (trace.line) {
+      let line = frame.querySelector(".message-location").sourceLine;
+      if (!checkText(trace.line, line)) {
+        ok(false, "console.trace() message is missing the line number: " +
+                  trace.line);
+        displayErrorContext(aRule, aElement);
+        return false;
+      }
     }
 
     aRule.category = CATEGORY_WEBDEV;
     aRule.severity = SEVERITY_LOG;
+    aRule.type = Messages.ConsoleTrace;
 
     return true;
   }
 
   function checkConsoleTime(aRule, aElement)
   {
     let elemText = aElement.textContent;
     let time = aRule.consoleTime;
@@ -1033,17 +1029,17 @@ function waitForMessages(aOptions)
     aRule.category = CATEGORY_WEBDEV;
     aRule.severity = SEVERITY_LOG;
 
     return true;
   }
 
   function checkSource(aRule, aElement)
   {
-    let location = aElement.querySelector(".location");
+    let location = aElement.querySelector(".message-location");
     if (!location) {
       return false;
     }
 
     if (!checkText(aRule.source.url, location.getAttribute("title"))) {
       return false;
     }
 
@@ -1085,26 +1081,33 @@ function waitForMessages(aOptions)
     if (aRule.consoleGroup && !checkConsoleGroup(aRule, aElement)) {
       return false;
     }
 
     if (aRule.source && !checkSource(aRule, aElement)) {
       return false;
     }
 
+    let partialMatch = !!(aRule.consoleTrace || aRule.consoleTime ||
+                          aRule.consoleTimeEnd);
+
     // The rule tries to match the newer types of messages, based on their
     // object constructor.
-    if (aRule.type && (!aElement._messageObject ||
-                       !(aElement._messageObject instanceof aRule.type))) {
-      return false;
+    if (aRule.type) {
+      if (!aElement._messageObject ||
+          !(aElement._messageObject instanceof aRule.type)) {
+        if (partialMatch) {
+          ok(false, "message type for rule: " + displayRule(aRule));
+          displayErrorContext(aRule, aElement);
+        }
+        return false;
+      }
+      partialMatch = true;
     }
 
-    let partialMatch = !!(aRule.consoleTrace || aRule.consoleTime ||
-                          aRule.consoleTimeEnd || aRule.type);
-
     if ("category" in aRule && aElement.category != aRule.category) {
       if (partialMatch) {
         is(aElement.category, aRule.category,
            "message category for rule: " + displayRule(aRule));
         displayErrorContext(aRule, aElement);
       }
       return false;
     }
@@ -1119,17 +1122,17 @@ function waitForMessages(aOptions)
     }
 
     if (aRule.category == CATEGORY_NETWORK && "url" in aRule &&
         !checkText(aRule.url, aElement.url)) {
       return false;
     }
 
     if ("repeats" in aRule) {
-      let repeats = aElement.querySelector(".repeats");
+      let repeats = aElement.querySelector(".message-repeats");
       if (!repeats || repeats.getAttribute("value") != aRule.repeats) {
         return false;
       }
     }
 
     if ("groupDepth" in aRule) {
       let timestamp = aElement.querySelector(".timestamp");
       let indent = (GROUP_INDENT * aRule.groupDepth) + "px";
@@ -1175,17 +1178,17 @@ function waitForMessages(aOptions)
     aRule.matched.add(aElement);
 
     return aRule.matched.size == count;
   }
 
   function onMessagesAdded(aEvent, aNewElements)
   {
     for (let elem of aNewElements) {
-      let location = elem.querySelector(".location");
+      let location = elem.querySelector(".message-location");
       if (location) {
         let url = location.title;
         // Prevent recursion with the browser console and any potential
         // messages coming from head.js.
         if (url.indexOf("browser/devtools/webconsole/test/head.js") != -1) {
           continue;
         }
       }

new file mode 100644
--- /dev/null
+++ b/browser/devtools/webconsole/test/test-bug_939783_console_trace_duplicates.html
@@ -0,0 +1,35 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <title>Web Console test for bug 939783 - different console.trace() calls
+      wrongly filtered as duplicates</title>
+    <!-- Any copyright is dedicated to the Public Domain.
+         http://creativecommons.org/publicdomain/zero/1.0/ -->
+<script type="application/javascript">
+function foo1() {
+  foo2();
+}
+
+function foo1b() {
+  foo2();
+}
+
+function foo2() {
+  foo3();
+}
+
+function foo3() {
+  console.trace();
+}
+
+foo1(); foo1();
+foo1b();
+
+</script>
+  </head>
+  <body>
+    <p>Web Console test for bug 939783 - different console.trace() calls
+      wrongly filtered as duplicates</p>
+  </body>
+</html>

--- a/browser/devtools/webconsole/webconsole.js
+++ b/browser/devtools/webconsole/webconsole.js
@@ -1051,17 +1051,17 @@ WebConsoleFrame.prototype = {
    * @param nsIDOMNode aOriginal
    *        The Original Node. The one being merged into.
    * @param nsIDOMNode aFiltered
    *        The node being filtered out because it is repeated.
    */
   mergeFilteredMessageNode:
   function WCF_mergeFilteredMessageNode(aOriginal, aFiltered)
   {
-    let repeatNode = aOriginal.getElementsByClassName("repeats")[0];
+    let repeatNode = aOriginal.getElementsByClassName("message-repeats")[0];
     if (!repeatNode) {
       return; // no repeat node, return early.
     }
 
     let occurrences = parseInt(repeatNode.getAttribute("value")) + 1;
     repeatNode.setAttribute("value", occurrences);
     repeatNode.textContent = occurrences;
     let str = l10n.getStr("messageRepeats.tooltip2");
@@ -1076,17 +1076,17 @@ WebConsoleFrame.prototype = {
    * @param nsIDOMNode aNode
    *        The message node to be filtered or not.
    * @returns nsIDOMNode|null
    *          Returns the duplicate node if the message was filtered, null
    *          otherwise.
    */
   _filterRepeatedMessage: function WCF__filterRepeatedMessage(aNode)
   {
-    let repeatNode = aNode.getElementsByClassName("repeats")[0];
+    let repeatNode = aNode.getElementsByClassName("message-repeats")[0];
     if (!repeatNode) {
       return null;
     }
 
     let uid = repeatNode._uid;
     let dupeNode = null;
 
     if (aNode.category == CATEGORY_CSS ||
@@ -1100,17 +1100,17 @@ WebConsoleFrame.prototype = {
               aNode.category == CATEGORY_JS) &&
              aNode.category != CATEGORY_NETWORK &&
              !aNode.classList.contains("inlined-variables-view")) {
       let lastMessage = this.outputNode.lastChild;
       if (!lastMessage) {
         return null;
       }
 
-      let lastRepeatNode = lastMessage.getElementsByClassName("repeats")[0];
+      let lastRepeatNode = lastMessage.getElementsByClassName("message-repeats")[0];
       if (lastRepeatNode && lastRepeatNode._uid == uid) {
         dupeNode = lastMessage;
       }
     }
 
     if (dupeNode) {
       this.mergeFilteredMessageNode(dupeNode, aNode);
       return dupeNode;
@@ -1186,58 +1186,31 @@ WebConsoleFrame.prototype = {
       case "error":
       case "exception":
       case "assert":
       case "debug": {
         let msg = new Messages.ConsoleGeneric(aMessage);
         node = msg.init(this.output).render().element;
         break;
       }
+      case "trace": {
+        let msg = new Messages.ConsoleTrace(aMessage);
+        node = msg.init(this.output).render().element;
+        break;
+      }
       case "dir": {
         body = { arguments: args };
         let clipboardArray = [];
         args.forEach((aValue) => {
           clipboardArray.push(VariablesView.getString(aValue));
         });
         clipboardText = clipboardArray.join(" ");
         break;
       }
 
-      case "trace": {
-        let filename = WebConsoleUtils.abbreviateSourceURL(aMessage.filename);
-        let functionName = aMessage.functionName ||
-                           l10n.getStr("stacktrace.anonymousFunction");
-
-        body = this.document.createElementNS(XHTML_NS, "a");
-        body.setAttribute("aria-haspopup", true);
-        body.href = "#";
-        body.draggable = false;
-        body.textContent = l10n.getFormatStr("stacktrace.outputMessage",
-                                             [filename, functionName,
-                                              sourceLine]);
-
-        this._addMessageLinkCallback(body, () => {
-          this.jsterm.openVariablesView({
-            rawObject: aMessage.stacktrace,
-            autofocus: true,
-          });
-        });
-
-        clipboardText = body.textContent + "\n";
-
-        aMessage.stacktrace.forEach(function(aFrame) {
-          clipboardText += aFrame.filename + " :: " +
-                           aFrame.functionName + " :: " +
-                           aFrame.lineNumber + "\n";
-        });
-
-        clipboardText = clipboardText.trimRight();
-        break;
-      }
-
       case "group":
       case "groupCollapsed":
         clipboardText = body = aMessage.groupName;
         this.groupDepth++;
         break;
 
       case "groupEnd":
         if (this.groupDepth > 0) {
@@ -1276,17 +1249,16 @@ WebConsoleFrame.prototype = {
     }
 
     // Release object actors for arguments coming from console API methods that
     // we ignore their arguments.
     switch (level) {
       case "group":
       case "groupCollapsed":
       case "groupEnd":
-      case "trace":
       case "time":
       case "timeEnd":
         for (let actor of objectActors) {
           this._releaseObject(actor);
         }
         objectActors.clear();
     }
 
@@ -1302,25 +1274,21 @@ WebConsoleFrame.prototype = {
         node.setAttribute("private", true);
       }
     }
 
     if (objectActors.size > 0) {
       node._objectActors = objectActors;
 
       if (!node._messageObject) {
-        let repeatNode = node.getElementsByClassName("repeats")[0];
+        let repeatNode = node.getElementsByClassName("message-repeats")[0];
         repeatNode._uid += [...objectActors].join("-");
       }
     }
 
-    if (level == "trace") {
-      node._stacktrace = aMessage.stacktrace;
-    }
-
     return node;
   },
 
   /**
    * Handle ConsoleAPICall objects received from the server. This method outputs
    * the window.console API call.
    *
    * @param object aMessage
@@ -2383,17 +2351,17 @@ WebConsoleFrame.prototype = {
       for (let actor of aNode._objectActors) {
         this._releaseObject(actor);
       }
       aNode._objectActors.clear();
     }
 
     if (aNode.category == CATEGORY_CSS ||
         aNode.category == CATEGORY_SECURITY) {
-      let repeatNode = aNode.getElementsByClassName("repeats")[0];
+      let repeatNode = aNode.getElementsByClassName("message-repeats")[0];
       if (repeatNode && repeatNode._uid) {
         delete this._repeatNodes[repeatNode._uid];
       }
     }
     else if (aNode._connectionId &&
              aNode.category == CATEGORY_NETWORK) {
       delete this._networkRequests[aNode._connectionId];
       this._releaseObject(aNode._connectionId);
@@ -2496,17 +2464,17 @@ WebConsoleFrame.prototype = {
     // Add the message repeats node only when needed.
     let repeatNode = null;
     if (aCategory != CATEGORY_INPUT &&
         aCategory != CATEGORY_OUTPUT &&
         aCategory != CATEGORY_NETWORK &&
         !(aCategory == CATEGORY_CSS && aSeverity == SEVERITY_LOG)) {
       repeatNode = this.document.createElementNS(XHTML_NS, "span");
       repeatNode.setAttribute("value", "1");
-      repeatNode.className = "repeats";
+      repeatNode.className = "message-repeats";
       repeatNode.textContent = 1;
       repeatNode._uid = [bodyNode.textContent, aCategory, aSeverity, aLevel,
                          aSourceURL, aSourceLine].join(":");
     }
 
     // Create the timestamp.
     let timestampNode = this.document.createElementNS(XHTML_NS, "span");
     timestampNode.className = "timestamp devtools-monospace";
@@ -2562,21 +2530,28 @@ WebConsoleFrame.prototype = {
    * Creates the anchor that displays the textual location of an incoming
    * message.
    *
    * @param string aSourceURL
    *        The URL of the source file responsible for the error.
    * @param number aSourceLine [optional]
    *        The line number on which the error occurred. If zero or omitted,
    *        there is no line number associated with this message.
+   * @param string aTarget [optional]
+   *        Tells which tool to open the link with, on click. Supported tools:
+   *        jsdebugger, styleeditor, scratchpad.
    * @return nsIDOMNode
    *         The new anchor element, ready to be added to the message node.
    */
-  createLocationNode: function WCF_createLocationNode(aSourceURL, aSourceLine)
+  createLocationNode:
+  function WCF_createLocationNode(aSourceURL, aSourceLine, aTarget)
   {
+    if (!aSourceURL) {
+      aSourceURL = "";
+    }
     let locationNode = this.document.createElementNS(XHTML_NS, "a");
     let filenameNode = this.document.createElementNS(XHTML_NS, "span");
 
     // Create the text, which consists of an abbreviated version of the URL
     // Scratchpad URLs should not be abbreviated.
     let filename;
     let fullURL;
     let isScratchpad = false;
@@ -2587,40 +2562,49 @@ WebConsoleFrame.prototype = {
       isScratchpad = true;
     }
     else {
       fullURL = aSourceURL.split(" -> ").pop();
       filename = WebConsoleUtils.abbreviateSourceURL(fullURL);
     }
 
     filenameNode.className = "filename";
-    filenameNode.textContent = " " + filename;
+    filenameNode.textContent = " " + (filename || l10n.getStr("unknownLocation"));
     locationNode.appendChild(filenameNode);
 
-    locationNode.href = isScratchpad ? "#" : fullURL;
+    locationNode.href = isScratchpad || !fullURL ? "#" : fullURL;
     locationNode.draggable = false;
+    locationNode.target = aTarget;
     locationNode.setAttribute("title", aSourceURL);
-    locationNode.className = "location theme-link devtools-monospace";
+    locationNode.className = "message-location theme-link devtools-monospace";
 
     // Make the location clickable.
-    this._addMessageLinkCallback(locationNode, () => {
-      if (isScratchpad) {
+    let onClick = () => {
+      let target = locationNode.target;
+      if (target == "scratchpad" || isScratchpad) {
         this.owner.viewSourceInScratchpad(aSourceURL);
+        return;
       }
-      else if (locationNode.parentNode.category == CATEGORY_CSS) {
+
+      let category = locationNode.parentNode.category;
+      if (target == "styleeditor" || category == CATEGORY_CSS) {
         this.owner.viewSourceInStyleEditor(fullURL, aSourceLine);
       }
-      else if (locationNode.parentNode.category == CATEGORY_JS ||
-               locationNode.parentNode.category == CATEGORY_WEBDEV) {
+      else if (target == "jsdebugger" ||
+               category == CATEGORY_JS || category == CATEGORY_WEBDEV) {
         this.owner.viewSourceInDebugger(fullURL, aSourceLine);
       }
       else {
         this.owner.viewSource(fullURL, aSourceLine);
       }
-    });
+    };
+
+    if (fullURL) {
+      this._addMessageLinkCallback(locationNode, onClick);
+    }
 
     if (aSourceLine) {
       let lineNumberNode = this.document.createElementNS(XHTML_NS, "span");
       lineNumberNode.className = "line-number";
       lineNumberNode.textContent = ":" + aSourceLine;
       locationNode.appendChild(lineNumberNode);
       locationNode.sourceLine = aSourceLine;
     }

--- a/browser/locales/en-US/chrome/browser/devtools/webconsole.properties
+++ b/browser/locales/en-US/chrome/browser/devtools/webconsole.properties
@@ -97,25 +97,23 @@ gcliterm.instanceLabel=Instance of %S
 # The 2nd line, from "function" to the end of the line, is a link to the
 # JavaScript debugger.
 reflow.messageWithNoLink=reflow: %Sms
 reflow.messageWithLink=reflow: %Sms\u0020
 reflow.messageLinkText=function %1$S, %2$S line %3$S
 
 # LOCALIZATION NOTE (stacktrace.anonymousFunction): this string is used to
 # display JavaScript functions that have no given name - they are said to be
-# anonymous. See also stacktrace.outputMessage.
+# anonymous. Test console.trace() in the webconsole.
 stacktrace.anonymousFunction=<anonymous>
 
-# LOCALIZATION NOTE (stacktrace.outputMessage): this string is used in the Web
-# Console output to identify a web developer call to console.trace(). The
-# stack trace of JavaScript function calls is displayed. In this minimal
-# message we only show the last call. Parameters: %1$S is the file name, %2$S
-# is the function name, %3$S is the line number.
-stacktrace.outputMessage=Stack trace from %1$S, function %2$S, line %3$S.
+# LOCALIZATION NOTE (unknownLocation): this string is used to
+# display messages with sources that have an unknown location, eg. from
+# console.trace() calls.
+unknownLocation=<unknown>
 
 # LOCALIZATION NOTE (timerStarted): this string is used to display the result
 # of the console.time() call. Parameters: %S is the name of the timer.
 timerStarted=%S: timer started
 
 # LOCALIZATION NOTE (timeEnd): this string is used to display the result of
 # the console.timeEnd() call. Parameters: %1$S is the name of the timer, %2$S
 # is the number of milliseconds.

--- a/browser/themes/shared/devtools/webconsole.inc.css
+++ b/browser/themes/shared/devtools/webconsole.inc.css
@@ -41,59 +41,59 @@ a {
 .message > .body {
   flex: 1 1 100%;
   white-space: pre-wrap;
   word-wrap: break-word;
   margin-top: 4px;
 }
 
 /* The red bubble that shows the number of times a message is repeated */
-.message > .repeats {
+.message-repeats {
   -moz-user-select: none;
   flex: 0 0 auto;
   margin: 2px 6px;
   padding: 0 6px;
   height: 1.25em;
   color: white;
   background-color: red;
   border-radius: 40px;
   font: message-box;
   font-size: 0.9em;
   font-weight: 600;
 }
 
-.message > .repeats[value="1"] {
+.message-repeats[value="1"] {
   display: none;
 }
 
-.message > .location {
+.message-location {
   -moz-margin-start: 6px;
   display: flex;
   flex: 0 0 auto;
   align-self: flex-start;
   justify-content: flex-end;
   width: 10em;
   margin-top: 4px;
   color: -moz-nativehyperlinktext;
   text-decoration: none;
+  white-space: nowrap;
 }
 
-.message > .location:hover,
-.message > .location:focus {
+.message-location:hover,
+.message-location:focus {
   text-decoration: underline;
 }
 
-.message > .location > .filename {
+.message-location > .filename {
   text-overflow: ellipsis;
   text-align: end;
   overflow: hidden;
-  white-space: nowrap;
 }
 
-.message > .location > .line-number {
+.message-location > .line-number {
   flex: 0 0 auto;
 }
 
 .jsterm-input-container {
   border-top-width: 1px;
   border-top-style: solid;
 }
 
@@ -331,16 +331,47 @@ a {
   font-size: 0.9em;
 }
 
 .navigation-marker .url {
   -moz-padding-end: 9px;
   text-decoration: none;
 }
 
+.consoleTrace .body > div {
+  display: flex;
+  margin-bottom: 5px;
+}
+
+.consoleTrace .title {
+  display: block;
+  flex: 1 1 auto;
+}
+
+.stacktrace {
+  list-style: none;
+  padding: 0 1em 0 1.5em;
+  margin: 0;
+  max-height: 10em;
+  overflow-y: auto;
+
+  border: 1px solid rgba(128, 128, 128, .5);
+  border-radius: 3px;
+}
+
+.stacktrace li {
+  display: flex;
+  margin: 0;
+}
+
+.stacktrace .function {
+  display: block;
+  flex: 1 1 auto;
+}
+
 /* Replace these values with CSS variables as available */
 .theme-dark .jsterm-input-container {
   background-color: #252c33; /* tabToolbarBackgroundColor */
   border-color: #131c26; /* mainBackgroundColor */
 }
 
 .theme-dark .jsterm-input-node {
   color: #8fa1b2; /* textColor */
@@ -353,16 +384,20 @@ a {
 .theme-dark .navigation-marker .url {
   background: #131c26; /* mainBackgroundColor */
 }
 
 .theme-dark .inlined-variables-view iframe {
   border-color: #333;
 }
 
+.theme-dark .stacktrace {
+  border-color: #333;
+}
+
 .theme-light .jsterm-input-container {
   background-color: #fff; /* mainBackgroundColor */
   border-color: ThreeDShadow;
 }
 
 .theme-light .jsterm-input-node {
   color: black; /* textColor */
 }
@@ -374,16 +409,20 @@ a {
 .theme-light .navigation-marker .url {
   background: #fff; /* mainBackgroundColor */
 }
 
 .theme-light .inlined-variables-view iframe {
   border-color: #ccc;
 }
 
+.theme-light .stacktrace {
+  border-color: #ccc;
+}
+
 @media (max-width: 500px) {
   .message > .timestamp {
     display: none;
   }
   .toolbarbutton-text {
     display: none;
   }
   .hud-console-filter-toolbar .webconsole-filter-button {