Revert of I cannot remember what the race here actually was.

include/core/SkDynamicAnnotations.h

Index: include/core/SkDynamicAnnotations.h
diff --git a/include/core/SkDynamicAnnotations.h b/include/core/SkDynamicAnnotations.h
index 108dd10f9c8798e0061d1bba9a50677118854b9c..e7710307f5532589a09b1f56d9b976cfdc373de7 100644
--- a/include/core/SkDynamicAnnotations.h
+++ b/include/core/SkDynamicAnnotations.h
@@ -66,4 +66,23 @@
 
 #endif
 
+// Can be used to wrap values that are intentionally racy, usually small mutable cached values, e.g.
+//   - SkMatrix type mask
+//   - SkPixelRef genIDs
+template <typename T>
+class SkTRacy {
+public:
+    operator const T() const {
+        return SK_ANNOTATE_UNPROTECTED_READ(fVal);
+    }
+
+    SkTRacy& operator=(const T& val) {
+        SK_ANNOTATE_UNPROTECTED_WRITE(&fVal, val);
+        return *this;
+    }
+
+private:
+    T fVal;
+};
+
 #endif//SkDynamicAnnotations_DEFINED