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

content/browser/aura/owned_mailbox.h

Index: content/browser/aura/owned_mailbox.h
diff --git a/content/browser/aura/owned_mailbox.h b/content/browser/aura/owned_mailbox.h
index ea1c242bf74ff9d385209871151a4e16a50d7d94..da431f09afa4c52a084c8451d9d49129292fe885 100644
--- a/content/browser/aura/owned_mailbox.h
+++ b/content/browser/aura/owned_mailbox.h
@@ -18,11 +18,11 @@ class OwnedMailbox : public base::RefCounted<OwnedMailbox>,
  public:
   explicit OwnedMailbox(GLHelper* gl_helper);
 
+  const gpu::Mailbox& mailbox() const { return mailbox_holder_.mailbox(); }
   uint32 texture_id() const { return texture_id_; }
-  uint32 sync_point() const { return sync_point_; }
-  const gpu::Mailbox& mailbox() const { return mailbox_; }
-
-  void UpdateSyncPoint(uint32 sync_point);
+  uint32 target() const { return mailbox_holder_.target(); }
+  uint32 sync_point() const { return mailbox_holder_.sync_point(); }
+  void set_sync_point(uint32 sync_point);
 
  protected:
   virtual ~OwnedMailbox();
@@ -33,8 +33,7 @@ class OwnedMailbox : public base::RefCounted<OwnedMailbox>,
   friend class base::RefCounted<OwnedMailbox>;
 
   uint32 texture_id_;
-  gpu::Mailbox mailbox_;
-  uint32 sync_point_;
+  gpu::MailboxHolder mailbox_holder_;
   GLHelper* gl_helper_;
 };