Move Singleton and related structs to namespace base

chrome/browser/policy/cloud/policy_header_service_factory.h

 // Copyright 2013 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_POLICY_CLOUD_POLICY_HEADER_SERVICE_FACTORY_H_
 #define CHROME_BROWSER_POLICY_CLOUD_POLICY_HEADER_SERVICE_FACTORY_H_
 
 #include "base/memory/singleton.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
@@ skipping 13 matching lines @@
 
   // Returns an instance of the PolicyHeaderServiceFactory singleton.
   static PolicyHeaderServiceFactory* GetInstance();
 
  protected:
   // BrowserContextKeyedServiceFactory implementation.
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* profile) const override;
 
  private:
-  friend struct DefaultSingletonTraits<PolicyHeaderServiceFactory>;
+  friend struct base::DefaultSingletonTraits<PolicyHeaderServiceFactory>;
 
   PolicyHeaderServiceFactory();
   ~PolicyHeaderServiceFactory() override;
 
   DISALLOW_COPY_AND_ASSIGN(PolicyHeaderServiceFactory);
 };
 
 }  // namespace policy
 
 #endif  // CHROME_BROWSER_POLICY_CLOUD_POLICY_HEADER_SERVICE_FACTORY_H_