Add proxy unique key management to GrOnFlushResourceProvider

Bug: skia:
Change-Id: I0c462e282ea6d78f22340546c03b357f1ba7666f
Reviewed-on: https://skia-review.googlesource.com/129140
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
2 files changed