Since a DirectBuffer11 may return different buffers from getBuffer
depending on the required buffer type and if the internal buffers are
dirty or not, the current serial is not reliable.  Use the actual buffer
object so that there can be no missmatch.

BUG=350581

Change-Id: I6ea1616273346117a17646edb68e6518e584f2b1
Reviewed-on: https://chromium-review.googlesource.com/189435Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>