The local dirty bits were sometimes not synced because gl::Texture doesn't
know that they exist.  Also fix calculation of when the workaround dirty
bits need to be set.

BUG=angleproject:1386

Change-Id: I3d9d1a01e5441be783190422093c485ea5da7aec
Reviewed-on: https://chromium-review.googlesource.com/396542Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>