Move Singleton and related structs to namespace base

ui/views/widget/desktop_aura/x11_desktop_handler.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 UI_VIEWS_WIDGET_DESKTOP_AURA_X11_DESKTOP_HANDLER_H_
 #define UI_VIEWS_WIDGET_DESKTOP_AURA_X11_DESKTOP_HANDLER_H_
 
 #include <X11/Xlib.h>
 // Get rid of a macro from Xlib.h that conflicts with Aura's RootWindow class.
 #undef RootWindow
 
 #include <vector>
 
 #include "ui/aura/env_observer.h"
 #include "ui/events/platform/platform_event_dispatcher.h"
 #include "ui/gfx/x/x11_atom_cache.h"
 #include "ui/gfx/x/x11_types.h"
 #include "ui/views/views_export.h"
 
+namespace base {
 template <typename T> struct DefaultSingletonTraits;
+}
 
 namespace views {
 
 // A singleton that owns global objects related to the desktop and listens for
 // X11 events on the X11 root window. Destroys itself when aura::Env is
 // deleted.
 class VIEWS_EXPORT X11DesktopHandler : public ui::PlatformEventDispatcher,
                                        public aura::EnvObserver {
  public:
   // Returns the singleton handler.
@@ skipping 72 matching lines @@
   ui::X11AtomCache atom_cache_;
 
   bool wm_supports_active_window_;
 
   DISALLOW_COPY_AND_ASSIGN(X11DesktopHandler);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WIDGET_DESKTOP_AURA_X11_DESKTOP_HANDLER_H_