Move Singleton and related structs to namespace base

chrome/browser/custom_handlers/protocol_handler_registry_factory.h

 // 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.
 
 #ifndef CHROME_BROWSER_CUSTOM_HANDLERS_PROTOCOL_HANDLER_REGISTRY_FACTORY_H_
 #define CHROME_BROWSER_CUSTOM_HANDLERS_PROTOCOL_HANDLER_REGISTRY_FACTORY_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 class Profile;
 class ProtocolHandlerRegistry;
+
+namespace base {
 template <typename T> struct DefaultSingletonTraits;
+}
 
 // Singleton that owns all ProtocolHandlerRegistrys and associates them with
 // Profiles. Listens for the Profile's destruction notification and cleans up
 // the associated ProtocolHandlerRegistry.
 class ProtocolHandlerRegistryFactory
     : public BrowserContextKeyedServiceFactory {
  public:
   // Returns the singleton instance of the ProtocolHandlerRegistryFactory.
   static ProtocolHandlerRegistryFactory* GetInstance();
 
   // Returns the ProtocolHandlerRegistry that provides intent registration for
   // |context|. Ownership stays with this factory object.
   static ProtocolHandlerRegistry* GetForBrowserContext(
       content::BrowserContext* context);
 
  protected:
   // BrowserContextKeyedServiceFactory implementation.
   bool ServiceIsCreatedWithBrowserContext() const override;
   content::BrowserContext* GetBrowserContextToUse(
       content::BrowserContext* context) const override;
   bool ServiceIsNULLWhileTesting() const override;
 
  private:
-  friend struct DefaultSingletonTraits<ProtocolHandlerRegistryFactory>;
+  friend struct base::DefaultSingletonTraits<ProtocolHandlerRegistryFactory>;
 
   ProtocolHandlerRegistryFactory();
   ~ProtocolHandlerRegistryFactory() override;
 
   // BrowserContextKeyedServiceFactory implementation.
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* profile) const override;
 
   DISALLOW_COPY_AND_ASSIGN(ProtocolHandlerRegistryFactory);
 };
 
 #endif  // CHROME_BROWSER_CUSTOM_HANDLERS_PROTOCOL_HANDLER_REGISTRY_FACTORY_H_