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: I23ead63c2f626fc94ccc216201fa8ddc5b652c1b
Reviewed-on: https://chromium-review.googlesource.com/189538Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>