Move Singleton and related structs to namespace base

chrome/browser/content_settings/host_content_settings_map_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/content_settings/host_content_settings_map_factory.h"
 
 #include "chrome/browser/profiles/off_the_record_profile_impl.h"
 #include "chrome/browser/profiles/profile.h"
 #include "components/content_settings/core/browser/host_content_settings_map.h"
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
@@ skipping 32 matching lines @@
 HostContentSettingsMap* HostContentSettingsMapFactory::GetForProfile(
     Profile* profile) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 
   return static_cast<HostContentSettingsMap*>(
       GetInstance()->GetServiceForBrowserContext(profile, true).get());
 }
 
 // static
 HostContentSettingsMapFactory* HostContentSettingsMapFactory::GetInstance() {
-  return Singleton<HostContentSettingsMapFactory>::get();
+  return base::Singleton<HostContentSettingsMapFactory>::get();
 }
 
 scoped_refptr<RefcountedKeyedService>
     HostContentSettingsMapFactory::BuildServiceInstanceFor(
     content::BrowserContext* context) const {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
 
   Profile* profile = static_cast<Profile*>(context);
   bool off_the_record = profile->GetProfileType() == Profile::INCOGNITO_PROFILE;
 
@@ skipping 25 matching lines @@
   }
 #endif // defined(ENABLE_SUPERVISED_USERS)
 
   return settings_map;
 }
 
 content::BrowserContext* HostContentSettingsMapFactory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
   return context;
 }