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

include/core/SkDynamicAnnotations.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkDynamicAnnotations_DEFINED
 #define SkDynamicAnnotations_DEFINED
 
@@ skipping 48 matching lines @@
 }
 
 #else  // !DYNAMIC_ANNOTATIONS_ENABLED
 
 #define SK_ANNOTATE_UNPROTECTED_READ(x) (x)
 #define SK_ANNOTATE_UNPROTECTED_WRITE(ptr, val) *(ptr) = (val)
 #define SK_ANNOTATE_BENIGN_RACE(ptr)
 
 #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