Move Singleton and related structs to namespace base

chrome/browser/ui/views/apps/keyboard_hook_handler.cc

 // Copyright 2014 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 "chrome/browser/ui/views/apps/keyboard_hook_handler.h"
 
 #include "base/memory/singleton.h"
 
 // TODO(sriramsr): Implement for other platforms.
 // Empty implementation for other platforms.
 void KeyboardHookHandler::Register(views::Widget* widget) {
 }
 
 void KeyboardHookHandler::Deregister(views::Widget* widget) {
 }
 
 // static
 KeyboardHookHandler* KeyboardHookHandler::GetInstance() {
-  return Singleton<KeyboardHookHandler,
-                   DefaultSingletonTraits<KeyboardHookHandler>>::get();
+  return base::Singleton<KeyboardHookHandler, base::DefaultSingletonTraits<
+                                                  KeyboardHookHandler>>::get();
 }