Move Singleton and related structs to namespace base

ui/gfx/win/singleton_hwnd.cc

 // 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.
 
 #include "ui/gfx/win/singleton_hwnd.h"
 
 #include "base/memory/singleton.h"
 #include "base/message_loop/message_loop.h"
 #include "ui/gfx/win/singleton_hwnd_observer.h"
 
 namespace gfx {
 
 // static
 SingletonHwnd* SingletonHwnd::GetInstance() {
-  return Singleton<SingletonHwnd>::get();
+  return base::Singleton<SingletonHwnd>::get();
 }
 
 BOOL SingletonHwnd::ProcessWindowMessage(HWND window,
                                          UINT message,
                                          WPARAM wparam,
                                          LPARAM lparam,
                                          LRESULT& result,
                                          DWORD msg_map_id) {
   FOR_EACH_OBSERVER(SingletonHwndObserver,
                     observer_list_,
@@ skipping 22 matching lines @@
 
 void SingletonHwnd::AddObserver(SingletonHwndObserver* observer) {
   observer_list_.AddObserver(observer);
 }
 
 void SingletonHwnd::RemoveObserver(SingletonHwndObserver* observer) {
   observer_list_.RemoveObserver(observer);
 }
 
 }  // namespace gfx