Move Singleton and related structs to namespace base

chrome/browser/favicon/fallback_icon_service_factory.h

 // Copyright 2015 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_FAVICON_FALLBACK_ICON_SERVICE_FACTORY_H_
 #define CHROME_BROWSER_FAVICON_FALLBACK_ICON_SERVICE_FACTORY_H_
 
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
+namespace base {
 template <typename T> struct DefaultSingletonTraits;
+}
 
 namespace content {
 class BrowserContext;
 }
 
 namespace favicon {
 class FallbackIconService;
 }
 
 // Singleton that owns all FallbackIconService and associates them with
 // BrowserContext instances.
 class FallbackIconServiceFactory : public BrowserContextKeyedServiceFactory {
  public:
   static favicon::FallbackIconService* GetForBrowserContext(
       content::BrowserContext* context);
 
   static FallbackIconServiceFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<FallbackIconServiceFactory>;
+  friend struct base::DefaultSingletonTraits<FallbackIconServiceFactory>;
 
   FallbackIconServiceFactory();
   ~FallbackIconServiceFactory() override;
 
   // BrowserContextKeyedServiceFactory:
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* context) const override;
   bool ServiceIsNULLWhileTesting() const override;
 
   DISALLOW_COPY_AND_ASSIGN(FallbackIconServiceFactory);
 };
 
 #endif  // CHROME_BROWSER_FAVICON_FALLBACK_ICON_SERVICE_FACTORY_H_