extensions: Cleanup class/struct fwd declarations

extensions/browser/guest_view/web_view/web_view_content_script_manager.h

 // Copyright 2015 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_GUEST_VIEW_WEB_VIEW_WEB_VIEW_CONTENT_SCRIPT_MANAGER_H
 #define EXTENSIONS_BROWSER_GUEST_VIEW_WEB_VIEW_WEB_VIEW_CONTENT_SCRIPT_MANAGER_H
 
 #include <map>
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/supports_user_data.h"
 #include "extensions/browser/user_script_loader.h"
 
 struct HostID;
 
 namespace content {
 class BrowserContext;
 class RenderFrameHost;
-class WebContents;
 }
 
 namespace extensions {
-class UserScript;
 
 // WebViewContentScriptManager manages the content scripts that each webview
 // guest adds and removes programmatically.
 class WebViewContentScriptManager : public base::SupportsUserData::Data,
                                     public UserScriptLoader::Observer {
  public:
   explicit WebViewContentScriptManager(
       content::BrowserContext* browser_context);
   ~WebViewContentScriptManager() override;
 
@@ skipping 63 matching lines @@
   std::vector<base::Closure> pending_scripts_loading_callbacks_;
 
   content::BrowserContext* browser_context_;
 
   DISALLOW_COPY_AND_ASSIGN(WebViewContentScriptManager);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_GUEST_VIEW_WEB_VIEW_WEB_VIEW_CONTENT_SCRIPT_MANAGER_H