- Instead of using a new Staging image everytime, we now
just use a DynamicBuffer that should be bit less wasteful.

Bug: angleproject:2480

Change-Id: I09edfb16f6ec49a0ca320d9e5dd9ce34e9dbf99e
Reviewed-on: https://chromium-review.googlesource.com/1059452
Commit-Queue: Luc Ferron <lucferron@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>