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

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

Index: third_party/WebKit/Source/platform/heap/TraceTraits.h
diff --git a/third_party/WebKit/Source/platform/heap/TraceTraits.h b/third_party/WebKit/Source/platform/heap/TraceTraits.h
index a56ccf1a0f3d4a5cebfea9e0068a3adaed65eb1d..f3e4bd07768dc90596cb45d1a9c9a03e463a5085 100644
--- a/third_party/WebKit/Source/platform/heap/TraceTraits.h
+++ b/third_party/WebKit/Source/platform/heap/TraceTraits.h
@@ -360,6 +360,14 @@ class TraceEagerlyTrait<Member<T>> {
 };
 
 template <typename T>
+class TraceEagerlyTrait<SameThreadCheckedMember<T>> {
+  STATIC_ONLY(TraceEagerlyTrait);
+
+ public:
+  static const bool value = TraceEagerlyTrait<T>::value;
+};
+
+template <typename T>
 class TraceEagerlyTrait<TraceWrapperMember<T>> {
   STATIC_ONLY(TraceEagerlyTrait);