Move Singleton and related structs to namespace base

chrome/browser/extensions/updater/extension_cache_impl.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_UPDATER_EXTENSION_CACHE_IMPL_H_
 #define CHROME_BROWSER_EXTENSIONS_UPDATER_EXTENSION_CACHE_IMPL_H_
 
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/callback_forward.h"
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "extensions/browser/updater/extension_cache.h"
 
+namespace base {
 template <typename T> struct DefaultSingletonTraits;
+}
 
 namespace extensions {
 
 class ExtensionCacheDelegate;
 class LocalExtensionCache;
 
 // Singleton call that caches extensions .crx files to share them between
 // multiple users and profiles on the machine.
 class ExtensionCacheImpl : public ExtensionCache,
                            public content::NotificationObserver {
@@ skipping 41 matching lines @@
 
   // Weak factory for callbacks.
   base::WeakPtrFactory<ExtensionCacheImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionCacheImpl);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_UPDATER_EXTENSION_CACHE_IMPL_H_