This path is hit for LUMA formats.

Only copy from storage to image when the storage is renderable,
otherwise it already has up-to-date data.  D3D9 cannot sync storage to
image without it being renderable.

Commit the region after CPU copies to make sure everything is
synchronized afterwards.

TEST=conformance/textures/canvas/tex-2d-luminance_alpha-luminance_alpha-unsigned_byte.html

BUG=angleproject:2192

Change-Id: I74ff748bd051a52cf472ca7ff77f54dfb5ba65b9
Reviewed-on: https://chromium-review.googlesource.com/730493
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>