Move Singleton and related structs to namespace base

chrome/browser/chromeos/events/xinput_hierarchy_changed_event_listener.h

 // Copyright (c) 2012 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.
 
 #ifndef CHROME_BROWSER_CHROMEOS_EVENTS_XINPUT_HIERARCHY_CHANGED_EVENT_LISTENER_H_
 #define CHROME_BROWSER_CHROMEOS_EVENTS_XINPUT_HIERARCHY_CHANGED_EVENT_LISTENER_H_
 
 #include "base/memory/singleton.h"
 #include "base/observer_list.h"
 #include "ui/events/platform/platform_event_observer.h"
 
 typedef union _XEvent XEvent;
 
 namespace chromeos {
 
 // XInputHierarchyChangedEventListener listens for an XI_HierarchyChanged event,
 // which is sent to Chrome when X detects a system or USB keyboard (or mouse),
 // then tells X to change the current XKB keyboard layout. Start by just calling
 // instance() to get it going.
 class XInputHierarchyChangedEventListener : public ui::PlatformEventObserver {
  public:
   static XInputHierarchyChangedEventListener* GetInstance();
 
   void Stop();
 
  private:
   // Defines the delete on exit Singleton traits we like.  Best to have this
   // and const/dest private as recommended for Singletons.
-  friend struct DefaultSingletonTraits<XInputHierarchyChangedEventListener>;
+  friend struct base::DefaultSingletonTraits<
+      XInputHierarchyChangedEventListener>;
 
   XInputHierarchyChangedEventListener();
   ~XInputHierarchyChangedEventListener() override;
 
   // ui::PlatformEventObserver:
   void WillProcessEvent(const ui::PlatformEvent& event) override;
   void DidProcessEvent(const ui::PlatformEvent& event) override;
 
   // Returns true if the event was processed, false otherwise.
   void ProcessedXEvent(XEvent* xevent);
 
   bool stopped_;
 
   DISALLOW_COPY_AND_ASSIGN(XInputHierarchyChangedEventListener);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_EVENTS_XINPUT_HIERARCHY_CHANGED_EVENT_LISTENER_H_