This will allow us to pass on extra information to the receiving end,
such as the specific texture levels that are dirty.

BUG=angleproject:1635

Change-Id: Idb7ca1d625499e50e7712c458b694f6e9bfc0595
Reviewed-on: https://chromium-review.googlesource.com/453382
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>