Make GrRRectBlurEffect use the thread-safe uniquely-keyed view cache (take 2)

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

Bug: 1108408
Change-Id: I710c75b73a395b2280abf0c5af528e0f6731326d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/311720
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/320917
diff --git a/tests/GrThreadSafeViewCacheTest.cpp b/tests/GrThreadSafeViewCacheTest.cpp
index 134d7e4..fe9b0f8 100644
--- a/tests/GrThreadSafeViewCacheTest.cpp
+++ b/tests/GrThreadSafeViewCacheTest.cpp
@@ -417,7 +417,7 @@
         GrSurfaceProxyView view;
 
         // We can "fail the lookup" to simulate a threaded race condition
-        if (auto view = threadSafeViewCache->find(key); !failLookup && view) {
+        if (view = threadSafeViewCache->find(key); !failLookup && view) {
             ++stats->fCacheHits;
             return view;
         }