Move Singleton and related structs to namespace base

chrome/browser/policy/cloud/policy_header_service_factory.cc

 // 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.
 
 #include "chrome/browser/policy/cloud/policy_header_service_factory.h"
 
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/profiles/profile.h"
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
@@ skipping 95 matching lines @@
   scoped_ptr<PolicyHeaderService> service = make_scoped_ptr(
       new PolicyHeaderService(device_management_service->GetServerUrl(),
                               kPolicyVerificationKeyHash,
                               user_store,
                               device_store));
   return new PolicyHeaderServiceWrapper(service.Pass());
 }
 
 // static
 PolicyHeaderServiceFactory* PolicyHeaderServiceFactory::GetInstance() {
-  return Singleton<PolicyHeaderServiceFactory>::get();
+  return base::Singleton<PolicyHeaderServiceFactory>::get();
 }
 
 }  // namespace policy