Switch to standard integer types in gpu/.

gpu/command_buffer/common/mailbox_holder.cc

 // Copyright 2014 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 <stdint.h>
+
 #include "gpu/command_buffer/common/mailbox_holder.h"
 
 namespace gpu {
 
 MailboxHolder::MailboxHolder() : texture_target(0) {}
 
 MailboxHolder::MailboxHolder(const gpu::Mailbox& mailbox,
                              const gpu::SyncToken& sync_token,
                              uint32_t texture_target)
     : mailbox(mailbox),
       sync_token(sync_token),
       texture_target(texture_target) {}
 
 }  // namespace gpu