content: Cleanup class/struct forward declarations

content/public/browser/message_port_provider.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 CONTENT_PUBLIC_BROWSER_MESSAGE_PORT_PROVIDER_H_
 #define CONTENT_PUBLIC_BROWSER_MESSAGE_PORT_PROVIDER_H_
 
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/singleton.h"
 #include "base/strings/string16.h"
 #include "content/common/content_export.h"
 
 namespace content {
 
 class AppWebMessagePortService;
 class WebContents;
-class MessagePortDelegate;
 
 // An interface consisting of methods that can be called to use Message ports.
 class CONTENT_EXPORT MessagePortProvider {
  public:
   // Posts a MessageEvent to the main frame using the given source and target
   // origins and data. The caller may also provide any message port ids as
   // part of the message.
   // See https://html.spec.whatwg.org/multipage/comms.html#messageevent for
   // further information on message events.
   // Should be called on UI thread.
   static void PostMessageToFrame(
       WebContents* web_contents,
       const base::string16& source_origin,
       const base::string16& target_origin,
       const base::string16& data,
       const std::vector<int>& ports);
 
 #if defined(OS_ANDROID)
   static content::AppWebMessagePortService* GetAppWebMessagePortService();
 #endif
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(MessagePortProvider);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_MESSAGE_PORT_PROVIDER_H_