Move Singleton and related structs to namespace base

content/browser/accessibility/ax_tree_id_registry.cc

 // Copyright 2014 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 "content/browser/accessibility/ax_tree_id_registry.h"
 
 #include "base/memory/singleton.h"
 
 namespace content {
 
 // static
 const AXTreeIDRegistry::AXTreeID AXTreeIDRegistry::kNoAXTreeID = -1;
 
 // static
 AXTreeIDRegistry* AXTreeIDRegistry::GetInstance() {
-  return Singleton<AXTreeIDRegistry>::get();
+  return base::Singleton<AXTreeIDRegistry>::get();
 }
 
 AXTreeIDRegistry::AXTreeID AXTreeIDRegistry::GetOrCreateAXTreeID(
     int process_id, int routing_id) {
   FrameID frame_id(process_id, routing_id);
   std::map<FrameID, AXTreeID>::iterator it;
   it = frame_to_ax_tree_id_map_.find(frame_id);
   if (it != frame_to_ax_tree_id_map_.end())
     return it->second;
 
@@ skipping 25 matching lines @@
 
 AXTreeIDRegistry::AXTreeIDRegistry() : ax_tree_id_counter_(-1) {
   // Always populate default desktop tree value (0 -> 0, 0).
   GetOrCreateAXTreeID(0, 0);
 }
 
 AXTreeIDRegistry::~AXTreeIDRegistry() {
 }
 
 }  // namespace content