By marking the images as dirty after binding a surface, the surface would
be cleared when it was first read or written to.

BUG=750813
BUG=angleproject:1635

Change-Id: Ic0d1c985151d55a0f1a1af67bb1edc4b0e8f2063
Reviewed-on: https://chromium-review.googlesource.com/598731
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>