Prepare to enable explicit gpu resource allocation

Change-Id: I407e45711c61831febbac3d3d3a88e3fdde92c5f
Reviewed-on: https://skia-review.googlesource.com/68212
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
12 files changed