Make GrRRectBlurEffect use the thread-safe uniquely-keyed view cache

This yields a ~8% performance improvement on OOP-R/DDL-like rendering of the simpleblurroundrect GM.

Bug: 1108408
Change-Id: I1ec9477dffe870e5973f8a334a65b1013a4ca3dd
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/311720
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
5 files changed