deleted file mode 100644
--- a/devtools/server/actors/eventlooplag.js
+++ /dev/null
@@ -1,59 +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";
-
-/**
- * The eventLoopLag actor emits "event-loop-lag" events when the event
- * loop gets unresponsive. The event comes with a "time" property (the
- * duration of the lag in milliseconds).
- */
-
-const {Ci} = require("chrome");
-const Services = require("Services");
-const {XPCOMUtils} = require("resource://gre/modules/XPCOMUtils.jsm");
-const {Actor, ActorClassWithSpec} = require("devtools/shared/protocol");
-const {eventLoopLagSpec} = require("devtools/shared/specs/eventlooplag");
-
-exports.EventLoopLagActor = ActorClassWithSpec(eventLoopLagSpec, {
-  _observerAdded: false,
-
-  /**
-   * Start tracking the event loop lags.
-   */
-  start: function() {
-    if (!this._observerAdded) {
-      Services.obs.addObserver(this, "event-loop-lag");
-      this._observerAdded = true;
-    }
-    return Services.appShell.startEventLoopLagTracking();
-  },
-
-  /**
-   * Stop tracking the event loop lags.
-   */
-  stop: function() {
-    if (this._observerAdded) {
-      Services.obs.removeObserver(this, "event-loop-lag");
-      this._observerAdded = false;
-    }
-    Services.appShell.stopEventLoopLagTracking();
-  },
-
-  destroy: function() {
-    this.stop();
-    Actor.prototype.destroy.call(this);
-  },
-
-  // nsIObserver
-
-  observe: function(subject, topic, data) {
-    if (topic == "event-loop-lag") {
-      // Forward event loop lag event
-      this.emit("event-loop-lag", data);
-    }
-  },
-
-  QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver]),
-});

--- a/devtools/server/actors/moz.build
+++ b/devtools/server/actors/moz.build
@@ -29,17 +29,16 @@ DevToolsModules(
     'common.js',
     'content.js',
     'css-properties.js',
     'csscoverage.js',
     'device.js',
     'emulation.js',
     'environment.js',
     'errordocs.js',
-    'eventlooplag.js',
     'frame.js',
     'framerate.js',
     'gcli.js',
     'heap-snapshot-file.js',
     'highlighters.css',
     'highlighters.js',
     'layout.js',
     'memory.js',

--- a/devtools/server/main.js
+++ b/devtools/server/main.js
@@ -490,21 +490,16 @@ var DebuggerServer = {
       constructor: "MemoryActor",
       type: { tab: true }
     });
     this.registerModule("devtools/server/actors/framerate", {
       prefix: "framerate",
       constructor: "FramerateActor",
       type: { tab: true }
     });
-    this.registerModule("devtools/server/actors/eventlooplag", {
-      prefix: "eventLoopLag",
-      constructor: "EventLoopLagActor",
-      type: { tab: true }
-    });
     this.registerModule("devtools/server/actors/reflow", {
       prefix: "reflow",
       constructor: "ReflowActor",
       type: { tab: true }
     });
     this.registerModule("devtools/server/actors/css-properties", {
       prefix: "cssProperties",
       constructor: "CssPropertiesActor",

deleted file mode 100644
--- a/devtools/server/tests/unit/test_eventlooplag_actor.js
+++ /dev/null
@@ -1,57 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-/**
- * Test the eventLoopLag actor.
- */
-
-"use strict";
-
-function run_test() {
-  let {EventLoopLagFront} = require("devtools/shared/fronts/eventlooplag");
-
-  DebuggerServer.init();
-  DebuggerServer.registerAllActors();
-
-  // As seen in EventTracer.cpp
-  let threshold = 20;
-  let interval = 10;
-
-  let front;
-  let client = new DebuggerClient(DebuggerServer.connectPipe());
-
-  // Start tracking event loop lags.
-  client.connect().then(function() {
-    client.listTabs().then(function(resp) {
-      front = new EventLoopLagFront(client, resp);
-      front.start().then(success => {
-        Assert.ok(success);
-        front.once("event-loop-lag", gotLagEvent);
-        executeSoon(lag);
-      });
-    });
-  });
-
-  // Force a lag
-  function lag() {
-    let start = new Date();
-    let duration = threshold + interval + 1;
-    while (true) {
-      if (((new Date()) - start) > duration) {
-        break;
-      }
-    }
-  }
-
-  // Got a lag event. The test will time out if the actor
-  // fails to detect the lag.
-  function gotLagEvent(time) {
-    info("lag: " + time);
-    Assert.ok(time >= threshold);
-    front.stop().then(() => {
-      finishClient(client);
-    });
-  }
-
-  do_test_pending();
-}

--- a/devtools/server/tests/unit/xpcshell.ini
+++ b/devtools/server/tests/unit/xpcshell.ini
@@ -127,19 +127,16 @@ skip-if = coverage # bug 1336670
 skip-if = true
 reason = bug 1104838
 [test_breakpoint-20.js]
 [test_breakpoint-21.js]
 [test_breakpoint-22.js]
 [test_conditional_breakpoint-01.js]
 [test_conditional_breakpoint-02.js]
 [test_conditional_breakpoint-03.js]
-[test_eventlooplag_actor.js]
-skip-if = true
-reason = only ran on B2G
 [test_listsources-01.js]
 [test_listsources-02.js]
 [test_listsources-03.js]
 [test_listsources-04.js]
 [test_new_source-01.js]
 [test_new_source-02.js]
 [test_sourcemaps-01.js]
 [test_sourcemaps-02.js]

deleted file mode 100644
--- a/devtools/shared/fronts/eventlooplag.js
+++ /dev/null
@@ -1,15 +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";
-
-const { Front, FrontClassWithSpec } = require("devtools/shared/protocol");
-const { eventLoopLagSpec } = require("devtools/shared/specs/eventlooplag");
-
-exports.EventLoopLagFront = FrontClassWithSpec(eventLoopLagSpec, {
-  initialize: function(client, form) {
-    Front.prototype.initialize.call(this, client);
-    this.actorID = form.eventLoopLagActor;
-    this.manage(this);
-  },
-});

--- a/devtools/shared/fronts/moz.build
+++ b/devtools/shared/fronts/moz.build
@@ -10,17 +10,16 @@ DevToolsModules(
     'addons.js',
     'animation.js',
     'call-watcher.js',
     'canvas.js',
     'css-properties.js',
     'csscoverage.js',
     'device.js',
     'emulation.js',
-    'eventlooplag.js',
     'framerate.js',
     'gcli.js',
     'highlighters.js',
     'inspector.js',
     'layout.js',
     'memory.js',
     'node.js',
     'perf.js',

deleted file mode 100644
--- a/devtools/shared/specs/eventlooplag.js
+++ /dev/null
@@ -1,31 +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";
-
-const { Arg, RetVal, generateActorSpec } = require("devtools/shared/protocol");
-
-const eventLoopLagSpec = generateActorSpec({
-  typeName: "eventLoopLag",
-
-  events: {
-    "event-loop-lag": {
-      type: "event-loop-lag",
-      // duration of the lag in milliseconds.
-      time: Arg(0, "number")
-    }
-  },
-
-  methods: {
-    start: {
-      request: {},
-      response: {success: RetVal("number")}
-    },
-    stop: {
-      request: {},
-      response: {}
-    }
-  }
-});
-
-exports.eventLoopLagSpec = eventLoopLagSpec;

--- a/devtools/shared/specs/index.js
+++ b/devtools/shared/specs/index.js
@@ -69,21 +69,16 @@ const Types = exports.__TypesForTests = 
     front: "devtools/shared/fronts/emulation",
   },
   /* environment has old fashion client and no front */
   {
     types: ["environment"],
     spec: "devtools/shared/specs/environment",
     front: null,
   },
-  {
-    types: ["eventLoopLag"],
-    spec: "devtools/shared/specs/eventlooplag",
-    front: "devtools/shared/fronts/eventlooplag",
-  },
   /* frame has old fashion client and no front */
   {
     types: ["frame"],
     spec: "devtools/shared/specs/frame",
     front: null,
   },
   {
     types: ["framerate"],

--- a/devtools/shared/specs/moz.build
+++ b/devtools/shared/specs/moz.build
@@ -12,17 +12,16 @@ DevToolsModules(
     'breakpoint.js',
     'call-watcher.js',
     'canvas.js',
     'css-properties.js',
     'csscoverage.js',
     'device.js',
     'emulation.js',
     'environment.js',
-    'eventlooplag.js',
     'frame.js',
     'framerate.js',
     'gcli.js',
     'heap-snapshot-file.js',
     'highlighters.js',
     'index.js',
     'inspector.js',
     'layout.js',