gdata: Make WeakPtrFactory the last parameter

chrome/browser/chromeos/gdata/gdata_file_system.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_FILE_SYSTEM_H_
 #define CHROME_BROWSER_CHROMEOS_GDATA_GDATA_FILE_SYSTEM_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 856 matching lines @@
   base::Timer update_timer_;
 
   // True if hosted documents should be hidden.
   bool hide_hosted_docs_;
 
   // The set of paths opened by OpenFile but not yet closed by CloseFile.
   std::set<FilePath> open_files_;
 
   scoped_ptr<PrefChangeRegistrar> pref_registrar_;
 
-  // WeakPtrFactory and WeakPtr bound to the UI thread.
-  base::WeakPtrFactory<GDataFileSystem> ui_weak_ptr_factory_;
-  base::WeakPtr<GDataFileSystem> ui_weak_ptr_;
-
   ObserverList<Observer> observers_;
 
   scoped_refptr<base::SequencedTaskRunner> blocking_task_runner_;
+
+  // 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<GDataFileSystem> weak_ptr_factory_;
 };
 
 }  // namespace gdata
 
 #endif  // CHROME_BROWSER_CHROMEOS_GDATA_GDATA_FILE_SYSTEM_H_