Add gpu::MailboxHolder to hold state for a gpu::Mailbox

cc/resources/single_release_callback.cc

 // Copyright 2013 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 "cc/resources/single_release_callback.h"
 
 #include "base/callback_helpers.h"
 #include "base/logging.h"
 
 namespace cc {
 
 SingleReleaseCallback::SingleReleaseCallback(const ReleaseCallback& callback)
     : has_been_run_(false), callback_(callback) {
   DCHECK(!callback_.is_null())
       << "Use a NULL SingleReleaseCallback for an empty callback.";
 }
 
 SingleReleaseCallback::~SingleReleaseCallback() {
   DCHECK(callback_.is_null() || has_been_run_)
       << "SingleReleaseCallback was never run.";
 }
 
-void SingleReleaseCallback::Run(unsigned sync_point, bool is_lost) {
+void SingleReleaseCallback::Run(uint32 sync_point, bool is_lost) {
   DCHECK(!has_been_run_) << "SingleReleaseCallback was run more than once.";
   has_been_run_ = true;
   callback_.Run(sync_point, is_lost);
 }
 
 }  // namespace cc