Move Singleton and related structs to namespace base

chrome/browser/prefs/pref_metrics_service.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/prefs/pref_metrics_service.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/metrics/histogram.h"
 #include "base/prefs/pref_registry_simple.h"
@@ skipping 194 matching lines @@
       histogram_name,
       1,
       boundary_value,
       boundary_value + 1,
       base::HistogramBase::kUmaTargetedHistogramFlag);
   histogram->Add(integer_value);
 }
 
 // static
 PrefMetricsService::Factory* PrefMetricsService::Factory::GetInstance() {
-  return Singleton<PrefMetricsService::Factory>::get();
+  return base::Singleton<PrefMetricsService::Factory>::get();
 }
 
 // static
 PrefMetricsService* PrefMetricsService::Factory::GetForProfile(
     Profile* profile) {
   return static_cast<PrefMetricsService*>(
       GetInstance()->GetServiceForBrowserContext(profile, true));
 }
 
 PrefMetricsService::Factory::Factory()
@@ skipping 16 matching lines @@
 }
 
 bool PrefMetricsService::Factory::ServiceIsNULLWhileTesting() const {
   return false;
 }
 
 content::BrowserContext* PrefMetricsService::Factory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
   return chrome::GetBrowserContextRedirectedInIncognito(context);
 }