heap: Enable concurrent marking for TraceWrapperV8Reference

Bug: 986235
Change-Id: Ifba84fb0880c668e3c1f6bc276d1f7beacea4261
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2332629Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#794226}

third_party/blink/renderer/platform/bindings/trace_wrapper_v8_reference.h

@@ -138,6 +138,14 @@ struct VectorTraits<blink::TraceWrapperV8Reference<T>>
   static const bool kCanClearUnusedSlotsWithMemset = true;
   static const bool kCanCopyWithMemcpy = false;
   static const bool kCanMoveWithMemcpy = false;
+  static constexpr bool kCanTraceConcurrently = true;
+};
+
+template <typename T>
+struct HashTraits<blink::TraceWrapperV8Reference<T>>
+    : GenericHashTraits<blink::TraceWrapperV8Reference<T>> {
+  STATIC_ONLY(HashTraits);
+  static constexpr bool kCanTraceConcurrently = true;
 };
 
 }  // namespace WTF