D3D11: Implement dirty bits for texture updates. BUG=angleproject:1387 Change-Id: I5f759c3dc60b53a5d4f8a1dd1f4a1d3d5330bfda Reviewed-on: https://chromium-review.googlesource.com/648487 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>