Make GrReleaseProcHelper an SkWeakRefCnt

Bug: skia:
Change-Id: Iccc22d477c17c4c58615e3f3bf9e551f9596b710
Reviewed-on: https://skia-review.googlesource.com/112562
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
1 file changed