extensions: Cleanup class/struct fwd declarations

extensions/browser/api/app_runtime/app_runtime_api.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 EXTENSIONS_BROWSER_API_APP_RUNTIME_APP_RUNTIME_API_H_
 #define EXTENSIONS_BROWSER_API_APP_RUNTIME_APP_RUNTIME_API_H_
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "extensions/common/constants.h"
 
 class GURL;
 
 namespace base {
 class DictionaryValue;
 }
 
 namespace content {
 class BrowserContext;
-class WebContents;
 }
 
 namespace extensions {
 
 namespace api {
 namespace app_runtime {
 struct ActionData;
 struct LaunchData;
 }
 }
@@ skipping 51 matching lines @@
   static void DispatchOnLaunchedEventWithUrl(content::BrowserContext* context,
                                              const Extension* extension,
                                              const std::string& handler_id,
                                              const GURL& url,
                                              const GURL& referrer_url);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_API_APP_RUNTIME_APP_RUNTIME_API_H_