Move Singleton and related structs to namespace base

chrome/browser/extensions/install_verifier_factory.cc

 // 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.
 
 #include "chrome/browser/extensions/install_verifier_factory.h"
 
 #include "chrome/browser/extensions/install_verifier.h"
 #include "chrome/browser/profiles/profile.h"
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
 #include "extensions/browser/extension_prefs.h"
 #include "extensions/browser/extension_prefs_factory.h"
 #include "extensions/browser/extension_registry_factory.h"
 #include "extensions/browser/extensions_browser_client.h"
 
 using content::BrowserContext;
 
 namespace extensions {
 
 // static
 InstallVerifier* InstallVerifierFactory::GetForBrowserContext(
     BrowserContext* context) {
   return static_cast<InstallVerifier*>(
       GetInstance()->GetServiceForBrowserContext(context, true));
 }
 
 // static
 InstallVerifierFactory* InstallVerifierFactory::GetInstance() {
-  return Singleton<InstallVerifierFactory>::get();
+  return base::Singleton<InstallVerifierFactory>::get();
 }
 
 InstallVerifierFactory::InstallVerifierFactory()
     : BrowserContextKeyedServiceFactory(
           "InstallVerifier",
           BrowserContextDependencyManager::GetInstance()) {
   DependsOn(ExtensionPrefsFactory::GetInstance());
   DependsOn(ExtensionRegistryFactory::GetInstance());
 }
 
 InstallVerifierFactory::~InstallVerifierFactory() {
 }
 
 KeyedService* InstallVerifierFactory::BuildServiceInstanceFor(
     BrowserContext* context) const {
   return new InstallVerifier(ExtensionPrefs::Get(context), context);
 }
 
 BrowserContext* InstallVerifierFactory::GetBrowserContextToUse(
     BrowserContext* context) const {
   // Redirected in incognito.
   return ExtensionsBrowserClient::Get()->GetOriginalContext(context);
 }
 
 }  // namespace extensions