This will allow us to manage the SurfaceSet in the GL layer.

BUG=angleproject:1684

Change-Id: Iab8243157710beab2667ef10275571078ce9ae8e
Reviewed-on: https://chromium-review.googlesource.com/424228Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>