DevTools: Add snapshot command log on the frontend.

Source/devtools/front_end/sdk/PaintProfiler.js

 /*
  * Copyright (C) 2013 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 43 matching lines @@
         LayerTreeAgent.replaySnapshot(this._id, firstStep || undefined, lastStep || undefined, wrappedCallback);
     },
 
     /**
      * @param {function(!Array.<!LayerTreeAgent.PaintProfile>=)} callback
      */
     profile: function(callback)
     {
         var wrappedCallback = InspectorBackend.wrapClientCallback(callback, "LayerTreeAgent.profileSnapshot(): ");
         LayerTreeAgent.profileSnapshot(this._id, 5, 1, wrappedCallback);
+    },
+
+    /**
+     * @param {?number} firstStep
+     * @param {?number} lastStep
+     * @param {function(!Array.<!Object>=)} callback
+     */
+    commandLog: function(firstStep, lastStep, callback)
+    {
+        var wrappedCallback = InspectorBackend.wrapClientCallback(callback, "LayerTreeAgent.snapshotCommandLog(): ");
+        LayerTreeAgent.snapshotCommandLog(this._id, firstStep || undefined, lastStep || undefined, wrappedCallback);
     }
 };