Fix D3D11 Hazard warnings in Debug.

BUG=angle:756
BUG=417424

Change-Id: I827f1db6bb0a3ba33f116e4cfbf8556da0e884d1
Reviewed-on: https://chromium-review.googlesource.com/221220
Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>