Implement the gamepad API in the IPC proxy

ppapi/host/host_message_context.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_MESSAGE_CONTEXT_H_
 #define PPAPI_HOST_HOST_MESSAGE_CONTEXT_H_
 
 #include "ipc/ipc_message.h"
 #include "ppapi/host/ppapi_host_export.h"
 #include "ppapi/proxy/resource_message_params.h"
 
 namespace ppapi {
 namespace host {
 
 // This context structure provides information about incoming resource message
 // call requests when passed to resources.
 struct PPAPI_HOST_EXPORT HostMessageContext {
-  explicit HostMessageContext(const ppapi::proxy::ResourceMessageCallParams& cp)
-      : params(cp) {
-  }
+  explicit HostMessageContext(
+      const ppapi::proxy::ResourceMessageCallParams& cp);
+  ~HostMessageContext();
+
+  // Returns a "reply params" struct with the same resource and sequence number
+  // as this request.
+  ppapi::proxy::ResourceMessageReplyParams MakeReplyParams();
 
   // The original call parameters passed to the resource message call.
   const ppapi::proxy::ResourceMessageCallParams& params;
 
   // The reply message. If the params has the callback flag set, this message
   // will be sent in reply. It is initialized to the empty message. If the
   // handler wants to send something else, it should just assign the message
   // it wants to this value.
   IPC::Message reply_msg;
 };
 
 }  // namespace host
 }  // namespace ppapi
 
 #endif  // PPAPI_HOST_HOST_MESSAGE_CONTEXT_H_