DevTools: Show asynchronous call stacks on frontend.

Source/devtools/front_end/Script.js

 /*
  * Copyright (C) 2008 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 208 matching lines @@
     updateLocations: function()
     {
         var items = this._locations.items();
         for (var i = 0; i < items.length; ++i)
             items[i].update();
     },
 
     /**
      * @param {WebInspector.DebuggerModel.Location} rawLocation
      * @param {function(!WebInspector.UILocation):(boolean|undefined)} updateDelegate
-     * @return {WebInspector.Script.Location}
+     * @return {!WebInspector.Script.Location}
      */
     createLiveLocation: function(rawLocation, updateDelegate)
     {
         console.assert(rawLocation.scriptId === this.scriptId);
         var location = new WebInspector.Script.Location(this, rawLocation, updateDelegate);
         this._locations.add(location);
         location.update();
         return location;
     },
 
@@ skipping 24 matching lines @@
     },
 
     dispose: function()
     {
         WebInspector.LiveLocation.prototype.dispose.call(this);
         this._script._locations.remove(this);
     },
 
     __proto__: WebInspector.LiveLocation.prototype
 }