ppapi: Cleanup class/struct forward declarations

ppapi/proxy/ppp_instance_proxy.h

 // Copyright (c) 2011 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_PROXY_PPP_INSTANCE_PROXY_H_
 #define PPAPI_PROXY_PPP_INSTANCE_PROXY_H_
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_resource.h"
 #include "ppapi/c/pp_var.h"
 #include "ppapi/proxy/interface_proxy.h"
 #include "ppapi/shared_impl/host_resource.h"
 #include "ppapi/shared_impl/ppp_instance_combined.h"
 
-struct PP_Rect;
-
 namespace ppapi {
 
 struct URLResponseInfoData;
 struct ViewData;
 
 namespace proxy {
 
 class PPP_Instance_Proxy : public InterfaceProxy {
  public:
   explicit PPP_Instance_Proxy(Dispatcher* dispatcher);
@@ skipping 23 matching lines @@
                                      int pending_loader_host_id,
                                      const URLResponseInfoData& data);
 
   std::unique_ptr<PPP_Instance_Combined> combined_interface_;
 };
 
 }  // namespace proxy
 }  // namespace ppapi
 
 #endif  // PPAPI_PROXY_PPP_INSTANCE_PROXY_H_