PPAPI: Refactor renderer side of browser host creation

ppapi/proxy/ppapi_messages.h

Index: ppapi/proxy/ppapi_messages.h
diff --git a/ppapi/proxy/ppapi_messages.h b/ppapi/proxy/ppapi_messages.h
index 766180b69d3a35c02ca53e5765cf1dc0f4c353de..89eb7bf90bb9884a3aec00a256c7fde541337687 100644
--- a/ppapi/proxy/ppapi_messages.h
+++ b/ppapi/proxy/ppapi_messages.h
@@ -429,6 +429,11 @@ IPC_STRUCT_TRAITS_BEGIN(ppapi::PpapiNaClPluginArgs)
   IPC_STRUCT_TRAITS_MEMBER(switch_values)
 IPC_STRUCT_TRAITS_END()
 
+IPC_STRUCT_TRAITS_BEGIN(ppapi::proxy::CompletedBrowserResourceHosts)
+  IPC_STRUCT_TRAITS_MEMBER(sequence_number)
+  IPC_STRUCT_TRAITS_MEMBER(host_ids)
+IPC_STRUCT_TRAITS_END()
+
 #if !defined(OS_NACL) && !defined(NACL_WIN64)
 
 IPC_STRUCT_TRAITS_BEGIN(ppapi::proxy::PPPDecryptor_Buffer)
@@ -1332,10 +1337,9 @@ IPC_MESSAGE_CONTROL5(
 // in the request and the IDs of the pending ResourceHosts which were created in
 // the browser. These IDs are only useful for the plugin which can attach to the
 // ResourceHosts in the browser.
-IPC_MESSAGE_ROUTED2(
+IPC_MESSAGE_ROUTED1(
     PpapiHostMsg_CreateResourceHostsFromHostReply,
-    int32_t /* sequence */,
-    std::vector<int> /* pending_host_ids */)
+    ppapi::proxy::CompletedBrowserResourceHosts /* completed_hosts */)
 
 //-----------------------------------------------------------------------------
 // Messages for resources using call/reply above.