Fix gyp build

runtime/vm/message_handler.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/message_handler.h"
 
 #include "vm/dart.h"
 #include "vm/lockers.h"
 #include "vm/object.h"
 #include "vm/object_store.h"
@@ skipping 315 matching lines @@
   return !oob_queue_->IsEmpty();
 }
 
 
 void MessageHandler::TaskCallback() {
   ASSERT(Isolate::Current() == NULL);
   MessageStatus status = kOK;
   bool run_end_callback = false;
   bool delete_me = false;
   EndCallback end_callback = NULL;
-  CallbackData callback_data = NULL;
+  CallbackData callback_data = 0;
   {
     // We will occasionally release and reacquire this monitor in this
     // function. Whenever we reacquire the monitor we *must* process
     // all pending OOB messages, or we may miss a request for vm
     // shutdown.
     MonitorLocker ml(&monitor_);
     if (ShouldPauseOnStart(kOK)) {
       if (!is_paused_on_start()) {
         PausedOnStartLocked(&ml, true);
       }
@@ skipping 239 matching lines @@
   handler_->oob_message_handling_allowed_ = false;
 }
 
 
 MessageHandler::AcquiredQueues::~AcquiredQueues() {
   ASSERT(handler_ != NULL);
   handler_->oob_message_handling_allowed_ = true;
 }
 
 }  // namespace dart