[DevTools] Add user metric action DeviceModeEnabled.

Source/devtools/front_end/host/UserMetrics.js

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 34 matching lines @@
 
 WebInspector.UserMetrics._ActionCodes = {
     WindowDocked: 1,
     WindowUndocked: 2,
     ScriptsBreakpointSet: 3,
     TimelineStarted: 4,
     ProfilesCPUProfileTaken: 5,
     ProfilesHeapProfileTaken: 6,
     AuditsStarted: 7,
     ConsoleEvaluated: 8,
-    FileSavedInWorkspace: 9
+    FileSavedInWorkspace: 9,
+    DeviceModeEnabled: 10
 }
 
 WebInspector.UserMetrics._PanelCodes = {
     elements: 1,
     resources: 2,
     network: 3,
     sources: 4,
     timeline: 5,
     profiles: 6,
     audits: 7,
@@ skipping 32 matching lines @@
 }
 
 WebInspector.UserMetrics._Recorder.prototype = {
     record: function()
     {
         InspectorFrontendHost.recordActionTaken(this._actionCode);
     }
 }
 
 WebInspector.userMetrics = new WebInspector.UserMetrics();