iwyu: Use callback_old.h where appropriate, part 1.

content/browser/webui/web_ui.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 CONTENT_BROWSER_WEBUI_WEB_UI_H_
 #define CONTENT_BROWSER_WEBUI_WEB_UI_H_
 #pragma once
 
 #include <map>
 #include <string>
 #include <vector>
 
-#include "base/callback.h"
+#include "base/callback_old.h"
 #include "base/compiler_specific.h"
 #include "base/string16.h"
 #include "content/common/page_transition_types.h"
 #include "ipc/ipc_channel.h"
 
 class DictionaryValue;
 class WebUIMessageHandler;
 class GURL;
 class ListValue;
 class Profile;
@@ skipping 202 matching lines @@
   // Extract a string value from a list Value.
   string16 ExtractStringValue(const ListValue* value);
 
   WebUI* web_ui_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(WebUIMessageHandler);
 };
 
 #endif  // CONTENT_BROWSER_WEBUI_WEB_UI_H_