chrome: Cleanup class/struct forward declarations

chrome/browser/thumbnails/thumbnail_list_source.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_THUMBNAILS_THUMBNAIL_LIST_SOURCE_H_
 #define CHROME_BROWSER_THUMBNAILS_THUMBNAIL_LIST_SOURCE_H_
 
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "components/history/core/browser/history_types.h"
 #include "content/public/browser/url_data_source.h"
 
 class Profile;
 
-namespace base {
-class RefCountedMemory;
-}
-
 namespace history {
 class TopSites;
 }
 
 namespace thumbnails {
 class ThumbnailService;
 }
 
 // ThumbnailListSource renders a webpage to list all thumbnails stored in
 // TopSites, along with all associated URLs. The thumbnail images are embedded
@@ skipping 31 matching lines @@
   scoped_refptr<history::TopSites> top_sites_;
 
   // For callbacks may be run after destruction.
   base::WeakPtrFactory<ThumbnailListSource> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ThumbnailListSource);
 };
 
 
 #endif  // CHROME_BROWSER_THUMBNAILS_THUMBNAIL_LIST_SOURCE_H_