ppapi: Cleanup class/struct forward declarations

ppapi/host/host_factory.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 PPAPI_HOST_HOST_FACTORY_H_
 #define PPAPI_HOST_HOST_FACTORY_H_
 
 #include <memory>
 
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_resource.h"
 
 namespace IPC {
 class Message;
 }
 
 namespace ppapi {
 
-namespace proxy {
-class ResourceMessageCallParams;
-}
-
 namespace host {
 
 class PpapiHost;
 class ResourceHost;
 
 // A host factory creates ResourceHosts for incoming create messages from
 // the plugin. This allows us to implement the hosts at the chrome/content
 // layer without the ppapi layer knowing about the details.
 class HostFactory {
  public:
   virtual ~HostFactory() {}
 
   virtual std::unique_ptr<ResourceHost> CreateResourceHost(
       PpapiHost* host,
       PP_Resource resource,
       PP_Instance instance,
       const IPC::Message& message) = 0;
 };
 
 }  // namespace host
 }  // namespace ppapi
 
 #endif  // PPAPI_HOST_HOST_FACTORY_H_