SameThreadCheckedMember<>: verify same-thread usage of heap references.

third_party/WebKit/Source/platform/heap/ThreadingTraits.h

Index: third_party/WebKit/Source/platform/heap/ThreadingTraits.h
diff --git a/third_party/WebKit/Source/platform/heap/ThreadingTraits.h b/third_party/WebKit/Source/platform/heap/ThreadingTraits.h
index 7dfffb5592a5a44adb0ef51e5f26e235d164163d..a58b796edc70a0688c11fe103dfbfbdbeb34ed75 100644
--- a/third_party/WebKit/Source/platform/heap/ThreadingTraits.h
+++ b/third_party/WebKit/Source/platform/heap/ThreadingTraits.h
@@ -19,6 +19,8 @@
 namespace blink {
 
 template <typename T>
+class SameThreadCheckedMember;
+template <typename T>
 class TraceWrapperMember;
 
 // ThreadAffinity indicates which threads objects can be used on. We
@@ -83,6 +85,12 @@ struct ThreadingTrait<Member<T>> {
 };
 
 template <typename T>
+struct ThreadingTrait<SameThreadCheckedMember<T>> {
+  STATIC_ONLY(ThreadingTrait);
+  static const ThreadAffinity Affinity = ThreadingTrait<T>::Affinity;
+};
+
+template <typename T>
 struct ThreadingTrait<TraceWrapperMember<T>> {
   STATIC_ONLY(ThreadingTrait);
   static const ThreadAffinity Affinity = ThreadingTrait<T>::Affinity;