Use callback_forward.h instead of callback.h where possible.

chrome/browser/prerender/prerender_tracker.h

 // Copyright (c) 2011 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_PRERENDER_PRERENDER_TRACKER_H_
 #define CHROME_BROWSER_PRERENDER_PRERENDER_TRACKER_H_
 #pragma once
 
 #include <map>
 #include <set>
 #include <vector>
 
-#include "base/callback.h"
+#include "base/callback_forward.h"
 #include "base/gtest_prod_util.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/non_thread_safe.h"
 #include "chrome/browser/prerender/prerender_final_status.h"
 #include "googleurl/src/gurl.h"
 
 namespace prerender {
 
 class PrerenderManager;
 struct RenderViewInfo;
@@ skipping 144 matching lines @@
   // |url_counter_| keeps track of the top-level URLs which are being
   // prerendered. It must only be accessed on the IO thread.
   URLCounter url_counter_;
 
   DISALLOW_COPY_AND_ASSIGN(PrerenderTracker);
 };
 
 }  // namespace prerender
 
 #endif  // CHROME_BROWSER_PRERENDER_PRERENDER_TRACKER_H_