chrome: Cleanup class/struct forward declarations

chrome/browser/extensions/api/tabs/tabs_api.h

 // Copyright (c) 2012 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_API_TABS_TABS_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_TABS_TABS_API_H_
 
 #include <string>
 #include <vector>
 
 #include "base/compiler_specific.h"
 #include "chrome/browser/extensions/chrome_extension_function.h"
 #include "chrome/browser/extensions/chrome_extension_function_details.h"
 #include "chrome/common/extensions/api/tabs.h"
 #include "components/zoom/zoom_controller.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "extensions/browser/api/execute_code_function.h"
 #include "extensions/browser/api/web_contents_capture_client.h"
 #include "extensions/browser/extension_function.h"
 #include "extensions/common/extension_resource.h"
 #include "extensions/common/user_script.h"
 #include "url/gurl.h"
 
 class GURL;
 class SkBitmap;
 class TabStripModel;
 
-namespace base {
-class DictionaryValue;
-}
-
 namespace content {
 class WebContents;
 }
 
 namespace ui {
 class ListSelectionModel;
 }
 
 namespace user_prefs {
 class PrefRegistrySyncable;
@@ skipping 293 matching lines @@
 
   // ExtensionFunction:
   ExtensionFunction::ResponseAction Run() override;
 
   DISALLOW_COPY_AND_ASSIGN(TabsDiscardFunction);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_TABS_TABS_API_H_