Handle DIRTY_BIT_LABEL in TextureGL::syncState. BUG=angleproject:1993 Change-Id: I495589e638443060ee8c140ee44a990e89f0ecdd Reviewed-on: https://chromium-review.googlesource.com/789491 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>