Remove SkRefCnt from GrGpu.

Change-Id: I6fcce1f83a7355327976dfd0cc0ce8567a10e345
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/756284
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
15 files changed