Move Singleton and related structs to namespace base

chrome/browser/chromeos/certificate_provider/certificate_provider_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_CHROMEOS_CERTIFICATE_PROVIDER_CERTIFICATE_PROVIDER_SERVICE_FACTORY_H_
 #define CHROME_BROWSER_CHROMEOS_CERTIFICATE_PROVIDER_CERTIFICATE_PROVIDER_SERVICE_FACTORY_H_
 
 #include "base/macros.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
+namespace base {
 template <typename T>
 struct DefaultSingletonTraits;
+}
 
 namespace content {
 class BrowserContext;
 }
 
 namespace chromeos {
 
 class CertificateProviderService;
 
 // Factory to create CertificateProviderService.
 class CertificateProviderServiceFactory
     : public BrowserContextKeyedServiceFactory {
  public:
   static CertificateProviderService* GetForBrowserContext(
       content::BrowserContext* context);
 
   static CertificateProviderServiceFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<CertificateProviderServiceFactory>;
+  friend struct base::DefaultSingletonTraits<CertificateProviderServiceFactory>;
 
   CertificateProviderServiceFactory();
 
   // BrowserContextKeyedServiceFactory:
   content::BrowserContext* GetBrowserContextToUse(
       content::BrowserContext* context) const override;
   bool ServiceIsNULLWhileTesting() const override;
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* context) const override;
 
   DISALLOW_COPY_AND_ASSIGN(CertificateProviderServiceFactory);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_CERTIFICATE_PROVIDER_CERTIFICATE_PROVIDER_SERVICE_FACTORY_H_