Pepper SRPC proxy style and type nits

ppapi/native_client/src/shared/ppapi_proxy/plugin_ppb_messaging.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 "native_client/src/shared/ppapi_proxy/plugin_ppb_messaging.h"
 
 #include "native_client/src/include/nacl_scoped_ptr.h"
 #include "native_client/src/include/portability.h"
 #include "native_client/src/shared/ppapi_proxy/object_serialize.h"
 #include "native_client/src/shared/ppapi_proxy/plugin_globals.h"
 #include "native_client/src/shared/ppapi_proxy/utility.h"
 #include "native_client/src/shared/srpc/nacl_srpc.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_var.h"
 #include "srpcgen/ppb_rpc.h"
 
 namespace ppapi_proxy {
 
 namespace {
 
 void PostMessage(PP_Instance instance, struct PP_Var message) {
-  DebugPrintf("PPB_Messaging::PostMessage: instance=%"NACL_PRIu32"\n",
+  DebugPrintf("PPB_Messaging::PostMessage: instance=%"NACL_PRId32"\n",
               instance);
   if (!ppapi_proxy::PPBCoreInterface()->IsMainThread())
     return;  // Only supported on main thread.
 
   uint32_t message_length = 0;
   nacl::scoped_array<char> message_bytes(Serialize(&message, 1,
                                                    &message_length));
   NaClSrpcError srpc_result =
       PpbMessagingRpcClient::PPB_Messaging_PostMessage(
           GetMainSrpcChannel(),
           instance,
           message_length,
           message_bytes.get());
   DebugPrintf("PPB_Messaging::PostMessage: %s\n",
               NaClSrpcErrorString(srpc_result));
 }
 
 }  // namespace
 
 const PPB_Messaging* PluginMessaging::GetInterface() {
   static const PPB_Messaging  messaging_interface = {
     PostMessage
   };
   return &messaging_interface;
 }
 
 }  // namespace ppapi_proxy