DevTools: Throttle file system refreshes on focus.

Source/devtools/front_end/sdk/ContentProviderBasedProjectDelegate.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 124 matching lines @@
         function innerCallback(success, newName)
         {
             if (success)
                 this._updateName(path, /** @type {string} */ (newName));
             callback(success, newName);
         }
     },
 
     /**
      * @param {string} path
+     * @param {function()=} callback
      */
-    refresh: function(path)
+    refresh: function(path, callback)
     {
+        if (callback)
+            callback();
     },
 
     /**
      * @param {string} path
      */
     excludeFolder: function(path)
     {
     },
 
     /**
@@ skipping 175 matching lines @@
         return this._contentProviders;
     },
 
     reset: function()
     {
         this._contentProviders = {};
         this._workspace.removeProject(this._id);
         this._projectStore = this._workspace.addProject(this._id, this);
     }
 }