Move Singleton and related structs to namespace base

chrome/browser/ui/apps/chrome_app_window_client.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_APPS_CHROME_APP_WINDOW_CLIENT_H_
 #define CHROME_BROWSER_UI_APPS_CHROME_APP_WINDOW_CLIENT_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "extensions/browser/app_window/app_window_client.h"
 
+namespace base {
 template <typename T>
 struct DefaultSingletonTraits;
+}
 
 // The implementation of AppWindowClient for Chrome.
 class ChromeAppWindowClient : public extensions::AppWindowClient {
  public:
   ChromeAppWindowClient();
   ~ChromeAppWindowClient() override;
 
   // Get the LazyInstance for ChromeAppWindowClient.
   static ChromeAppWindowClient* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<ChromeAppWindowClient>;
+  friend struct base::DefaultSingletonTraits<ChromeAppWindowClient>;
 
   // extensions::AppWindowClient
   extensions::AppWindow* CreateAppWindow(
       content::BrowserContext* context,
       const extensions::Extension* extension) override;
   extensions::NativeAppWindow* CreateNativeAppWindow(
       extensions::AppWindow* window,
       extensions::AppWindow::CreateParams* params) override;
   void OpenDevToolsWindow(content::WebContents* web_contents,
                           const base::Closure& callback) override;
   bool IsCurrentChannelOlderThanDev() override;
 
   // Implemented in platform specific code.
   static extensions::NativeAppWindow* CreateNativeAppWindowImpl(
       extensions::AppWindow* window,
       const extensions::AppWindow::CreateParams& params);
 
   DISALLOW_COPY_AND_ASSIGN(ChromeAppWindowClient);
 };
 
 #endif  // CHROME_BROWSER_UI_APPS_CHROME_APP_WINDOW_CLIENT_H_