Patch up ref counting of proxies

Bug: skia:
Change-Id: If746283d788368bf7aad6d285f181d8531768e61
Reviewed-on: https://skia-review.googlesource.com/70024
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
4 files changed