Revert of fAddedToCache doesn't need to be atomic.

include/core/SkPixelRef.h

Index: include/core/SkPixelRef.h
diff --git a/include/core/SkPixelRef.h b/include/core/SkPixelRef.h
index daf6af1438cba437569da834722fce7c7771d083..01303e5be5f1d156f235c336a1348f976152257a 100644
--- a/include/core/SkPixelRef.h
+++ b/include/core/SkPixelRef.h
@@ -248,7 +248,7 @@
     // Call when this pixelref is part of the key to a resourcecache entry. This allows the cache
     // to know automatically those entries can be purged when this pixelref is changed or deleted.
     void notifyAddedToCache() {
-        fAddedToCache = true;
+        fAddedToCache.store(true);
     }
 
 protected:
@@ -321,7 +321,7 @@
 
     mutable SkAtomic<uint32_t> fGenerationID;
     mutable SkAtomic<bool>     fUniqueGenerationID;
-    bool fAddedToCache;
+    SkAtomic<bool>             fAddedToCache;
 #ifdef SK_BUILD_FOR_ANDROID_FRAMEWORK
     const uint32_t fStableID;
 #endif