GL: Use dirty bits for texture and sampler bindings. In StateManagerGL, use the texture, sampler and program binding dirty bits to set a dirty bool that is checked once per draw call. This completes the GL back-end texture dirty bits. BUG=angleproject:1387 Change-Id: I619a89bf98ded5e55353f6ca44e814605f7ce492 Reviewed-on: https://chromium-review.googlesource.com/648055 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>