gdata: Make WeakPtrFactory the last parameter

chrome/browser/chromeos/gdata/gdata_sync_client.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_CHROMEOS_GDATA_GDATA_SYNC_CLIENT_H_
 #define CHROME_BROWSER_CHROMEOS_GDATA_GDATA_SYNC_CLIENT_H_
 
 #include <deque>
 #include <string>
 #include "base/callback.h"
@@ skipping 178 matching lines @@
   // thread. Note that this class does not use a lock to protect |queue_| as
   // all methods touching |queue_| run on the UI thread.
   std::deque<SyncTask> queue_;
 
   // The delay is used for delaying processing SyncTasks in DoSyncLoop().
   base::TimeDelta delay_;
 
   // True if the sync loop is running.
   bool sync_loop_is_running_;
 
+  // Note: This should remain the last member so it'll be destroyed and
+  // invalidate its weak pointers before any other members are destroyed.
   base::WeakPtrFactory<GDataSyncClient> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(GDataSyncClient);
 };
 
 }  // namespace gdata
 
 #endif  // CHROME_BROWSER_CHROMEOS_GDATA_GDATA_SYNC_CLIENT_H_