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

cc/resources/texture_mailbox_deleter.h

 // 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.
 
 #ifndef CC_RESOURCES_TEXTURE_MAILBOX_DELETER_H_
 #define CC_RESOURCES_TEXTURE_MAILBOX_DELETER_H_
 
 #include "base/memory/weak_ptr.h"
 #include "cc/base/cc_export.h"
 #include "cc/base/scoped_ptr_vector.h"
@@ skipping 14 matching lines @@
   // due to the compositor shutting down, then the ReleaseCallback will
   // become a no-op and the texture will be deleted immediately on the
   // impl thread, along with dropping the reference to the ContextProvider.
   scoped_ptr<SingleReleaseCallback> GetReleaseCallback(
       const scoped_refptr<ContextProvider>& context_provider,
       unsigned texture_id);
 
  private:
   // Runs the |impl_callback| to delete the texture and removes the callback
   // from the |impl_callbacks_| list.
-  void RunDeleteTextureOnImplThread(
-      SingleReleaseCallback* impl_callback,
-      unsigned sync_point,
-      bool is_lost);
+  void RunDeleteTextureOnImplThread(SingleReleaseCallback* impl_callback,
+                                    uint32 sync_point,
+                                    bool is_lost);
 
   ScopedPtrVector<SingleReleaseCallback> impl_callbacks_;
   base::WeakPtrFactory<TextureMailboxDeleter> weak_ptr_factory_;
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_TEXTURE_MAILBOX_DELETER_H_