Implement the gamepad API in the IPC proxy

ppapi/host/ppapi_host.cc

 // 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.
 
 #include "ppapi/host/ppapi_host.h"
 
 #include "base/logging.h"
 #include "ppapi/c/pp_errors.h"
 #include "ppapi/host/host_factory.h"
 #include "ppapi/host/host_message_context.h"
@@ skipping 73 matching lines @@
     const IPC::Message& nested_msg) {
   HostMessageContext context(params);
   proxy::ResourceMessageReplyParams reply_params(params.pp_resource(),
                                                  params.sequence());
 
   ResourceHost* resource_host = GetResourceHost(params.pp_resource());
   if (resource_host) {
     reply_params.set_result(resource_host->OnResourceMessageReceived(
         nested_msg, &context));
 
-    // Sanity check the resource handler.
+    // Sanity check the resource handler. Note if the result was
+    // "completion pending" the resource host may have already sent the reply.
     if (reply_params.result() == PP_OK_COMPLETIONPENDING) {
       // Message handler should have only returned a pending result if a
       // response will be sent to the plugin.
       DCHECK(params.has_callback());
 
       // Message handler should not have written a message to be returned if
       // completion is pending.
       DCHECK(context.reply_msg.type() == 0);
     } else if (!params.has_callback()) {
       // When no response is required, the message handler should not have
@@ skipping 35 matching lines @@
   resources_.erase(found);
 }
 
 ResourceHost* PpapiHost::GetResourceHost(PP_Resource resource) {
   ResourceMap::iterator found = resources_.find(resource);
   return found == resources_.end() ? NULL : found->second.get();
 }
 
 }  // namespace host
 }  // namespace ppapi