Added implementation of SyncEventObserver to route events to Javascript Extension.

chrome/browser/sync_file_system/sync_event_observer.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_SYNC_FILE_SYSTEM_SYNC_EVENT_OBSERVER_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_SYNC_EVENT_OBSERVER_H_
 
 #include <string>
 
 #include "webkit/fileapi/syncable/sync_operation_type.h"
 
+class GURL;
+
 namespace fileapi {
 class FileSystemURL;
 }
 
 namespace sync_file_system {
 
 class SyncEventObserver {
  public:
   typedef fileapi::SyncOperationType SyncOperationType;
 
@@ skipping 30 matching lines @@
   virtual void OnFileSynced(const fileapi::FileSystemURL& url,
                             fileapi::SyncOperationType operation) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SyncEventObserver);
 };
 
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_SYNC_EVENT_OBSERVER_H_