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

chrome/browser/spellchecker/spellchecker_platform_engine.h

 // Copyright (c) 2009 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.
 
 // This file defines the interface that any platform-specific spellchecker
 // needs to implement in order to be used by the browser.
 
 #ifndef CHROME_BROWSER_SPELLCHECKER_SPELLCHECKER_PLATFORM_ENGINE_H_
 #define CHROME_BROWSER_SPELLCHECKER_SPELLCHECKER_PLATFORM_ENGINE_H_
 #pragma once
 
 #include <string>
 #include <vector>
 
-#include "base/callback.h"
+#include "base/callback_forward.h"
 #include "base/string16.h"
 
 class BrowserMessageFilter;
 
 namespace SpellCheckerPlatform {
 
 // Get the languages supported by the platform spellchecker and store them in
 // |spellcheck_languages|. Note that they must be converted to
 // Chromium style codes (en-US not en_US). See spellchecker.cc for a full list.
 void GetAvailableLanguages(std::vector<std::string>* spellcheck_languages);
@@ skipping 63 matching lines @@
 // not be null.
 void RequestTextCheck(int route_id,
                       int identifier,
                       int document_tag,
                       const string16& text,
                       BrowserMessageFilter* destination);
 
 }  // namespace SpellCheckerPlatform
 
 #endif  // CHROME_BROWSER_SPELLCHECKER_SPELLCHECKER_PLATFORM_ENGINE_H_