--- a/b2g/chrome/content/devtools/hud.js
+++ b/b2g/chrome/content/devtools/hud.js
@@ -20,17 +20,17 @@ XPCOMUtils.defineLazyGetter(this, 'Debug
   return devtools.require('devtools/shared/client/main').DebuggerClient;
 });
 
 XPCOMUtils.defineLazyGetter(this, 'WebConsoleUtils', function() {
   return devtools.require('devtools/shared/webconsole/utils').Utils;
 });
 
 XPCOMUtils.defineLazyGetter(this, 'EventLoopLagFront', function() {
-  return devtools.require('devtools/server/actors/eventlooplag').EventLoopLagFront;
+  return devtools.require('devtools/shared/fronts/eventlooplag').EventLoopLagFront;
 });
 
 XPCOMUtils.defineLazyGetter(this, 'PerformanceEntriesFront', function() {
   return devtools.require('devtools/server/actors/performance-entries').PerformanceEntriesFront;
 });
 
 XPCOMUtils.defineLazyGetter(this, 'MemoryFront', function() {
   return devtools.require('devtools/server/actors/memory').MemoryFront;

--- a/devtools/server/actors/eventlooplag.js
+++ b/devtools/server/actors/eventlooplag.js
@@ -8,74 +8,53 @@
  * 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 protocol = require("devtools/shared/protocol");
-const {method, Arg, RetVal} = protocol;
+const {Actor, ActorClassWithSpec} = require("devtools/shared/protocol");
 const events = require("sdk/event/core");
-
-var EventLoopLagActor = exports.EventLoopLagActor = protocol.ActorClass({
-
-  typeName: "eventLoopLag",
+const {eventLoopLagSpec} = require("devtools/shared/specs/eventlooplag");
 
+var EventLoopLagActor = exports.EventLoopLagActor = ActorClassWithSpec(eventLoopLagSpec, {
   _observerAdded: false,
 
-  events: {
-    "event-loop-lag" : {
-      type: "event-loop-lag",
-      time: Arg(0, "number") // duration of the lag in milliseconds.
-    }
-  },
-
   /**
    * Start tracking the event loop lags.
    */
-  start: method(function () {
+  start: function () {
     if (!this._observerAdded) {
       Services.obs.addObserver(this, "event-loop-lag", false);
       this._observerAdded = true;
     }
     return Services.appShell.startEventLoopLagTracking();
-  }, {
-    request: {},
-    response: {success: RetVal("number")}
-  }),
+  },
 
   /**
    * Stop tracking the event loop lags.
    */
-  stop: method(function () {
+  stop: function () {
     if (this._observerAdded) {
       Services.obs.removeObserver(this, "event-loop-lag");
       this._observerAdded = false;
     }
     Services.appShell.stopEventLoopLagTracking();
-  }, {request: {}, response: {}}),
+  },
 
   destroy: function () {
     this.stop();
-    protocol.Actor.prototype.destroy.call(this);
+    Actor.prototype.destroy.call(this);
   },
 
   // nsIObserver
 
   observe: function (subject, topic, data) {
     if (topic == "event-loop-lag") {
       // Forward event loop lag event
       events.emit(this, "event-loop-lag", data);
     }
   },
 
   QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver]),
 });
-
-exports.EventLoopLagFront = protocol.FrontClass(EventLoopLagActor, {
-  initialize: function (client, form) {
-    protocol.Front.prototype.initialize.call(this, client);
-    this.actorID = form.eventLoopLagActor;
-    this.manage(this);
-  },
-});

--- a/devtools/server/tests/unit/test_eventlooplag_actor.js
+++ b/devtools/server/tests/unit/test_eventlooplag_actor.js
@@ -4,17 +4,17 @@
 /**
  * Test the eventLoopLag actor.
  */
 
 "use strict";
 
 function run_test()
 {
-  let {EventLoopLagFront} = require("devtools/server/actors/eventlooplag");
+  let {EventLoopLagFront} = require("devtools/shared/fronts/eventlooplag");
 
   DebuggerServer.init();
   DebuggerServer.addBrowserActors();
 
   // As seen in EventTracer.cpp
   let threshold = 20;
   let interval = 10;
 

new file mode 100644
--- /dev/null
+++ b/devtools/shared/fronts/eventlooplag.js
@@ -0,0 +1,15 @@
+/* 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
@@ -10,16 +10,17 @@ DevToolsModules(
     'animation.js',
     'call-watcher.js',
     'canvas.js',
     'css-properties.js',
     'csscoverage.js',
     'device.js',
     'director-manager.js',
     'director-registry.js',
+    'eventlooplag.js',
     'framerate.js',
     'gcli.js',
     'highlighters.js',
     'inspector.js',
     'layout.js',
     'memory.js',
     'performance-recording.js',
     'performance.js',

new file mode 100644
--- /dev/null
+++ b/devtools/shared/specs/eventlooplag.js
@@ -0,0 +1,31 @@
+/* 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/moz.build
+++ b/devtools/shared/specs/moz.build
@@ -12,16 +12,17 @@ DevToolsModules(
     'call-watcher.js',
     'canvas.js',
     'css-properties.js',
     'csscoverage.js',
     'device.js',
     'director-manager.js',
     'director-registry.js',
     'environment.js',
+    'eventlooplag.js',
     'frame.js',
     'framerate.js',
     'gcli.js',
     'heap-snapshot-file.js',
     'highlighters.js',
     'inspector.js',
     'layout.js',
     'memory.js',