Move Singleton and related structs to namespace base

content/child/child_io_surface_manager_mac.h

 // 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.
 
 #ifndef CONTENT_CHILD_CHILD_IO_SURFACE_MANAGER_MAC_H_
 #define CONTENT_CHILD_CHILD_IO_SURFACE_MANAGER_MAC_H_
 
 #include "base/mac/scoped_mach_port.h"
 #include "base/macros.h"
 #include "base/memory/singleton.h"
@@ skipping 27 matching lines @@
 
   // Set the token used when communicating with the Mach service.
   // Note: This can be called on any thread but must happen before the
   // thread-safe IOSurfaceManager interface is used. It is the responsibility
   // of users of this class to ensure there are no races.
   void set_token(const IOSurfaceManagerToken& token) {
     token_ = token;
   }
 
  private:
-  friend struct DefaultSingletonTraits<ChildIOSurfaceManager>;
+  friend struct base::DefaultSingletonTraits<ChildIOSurfaceManager>;
 
   ChildIOSurfaceManager();
   ~ChildIOSurfaceManager() override;
 
   base::mac::ScopedMachSendRight service_port_;
   IOSurfaceManagerToken token_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildIOSurfaceManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_CHILD_IO_SURFACE_MANAGER_MAC_H_