Move Singleton and related structs to namespace base

extensions/browser/app_window/app_window_registry.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 EXTENSIONS_BROWSER_APP_WINDOW_APP_WINDOW_REGISTRY_H_
 #define EXTENSIONS_BROWSER_APP_WINDOW_APP_WINDOW_REGISTRY_H_
 
 #include <list>
 #include <set>
 #include <string>
@@ skipping 93 matching lines @@
 
   class Factory : public BrowserContextKeyedServiceFactory {
    public:
     static AppWindowRegistry* GetForBrowserContext(
         content::BrowserContext* context,
         bool create);
 
     static Factory* GetInstance();
 
    private:
-    friend struct DefaultSingletonTraits<Factory>;
+    friend struct base::DefaultSingletonTraits<Factory>;
 
     Factory();
     ~Factory() override;
 
     // BrowserContextKeyedServiceFactory
     KeyedService* BuildServiceInstanceFor(
         content::BrowserContext* context) const override;
     bool ServiceIsCreatedWithBrowserContext() const override;
     bool ServiceIsNULLWhileTesting() const override;
     content::BrowserContext* GetBrowserContextToUse(
@@ skipping 23 matching lines @@
   content::BrowserContext* context_;
   AppWindowList app_windows_;
   InspectedWindowSet inspected_windows_;
   base::ObserverList<Observer> observers_;
   base::Callback<void(content::DevToolsAgentHost*, bool)> devtools_callback_;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_APP_WINDOW_APP_WINDOW_REGISTRY_H_