This paves the way for a dirty bits implementation for Textures, and
also will allow more precise ordering of the state update in D3D11.

The latter becomes important when moving the shader application.
Because the texture update can affect the built-in driver uniforms,
we neeed to update textures before we update the uniforms.

BUG=angleproject:1156
BUG=angleproject:1387

Change-Id: I995e095517c598d8672c6400d08a430da0e8339b
Reviewed-on: https://chromium-review.googlesource.com/580361Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>