Tracing HeapListHashSet<> iterators.

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

Index: third_party/WebKit/Source/platform/heap/HeapAllocator.h
diff --git a/third_party/WebKit/Source/platform/heap/HeapAllocator.h b/third_party/WebKit/Source/platform/heap/HeapAllocator.h
index 7d23b2cb0436195b7862bd7d53019fb0e06ad7e8..004de052e56db7d697d52e0c7a58efaeff150f03 100644
--- a/third_party/WebKit/Source/platform/heap/HeapAllocator.h
+++ b/third_party/WebKit/Source/platform/heap/HeapAllocator.h
@@ -737,6 +737,26 @@ struct IsGarbageCollectedType<
   static const bool value = true;
 };
 
+template <typename Set>
+struct IsGarbageCollectedType<ListHashSetIterator<Set>> {
+  static const bool value = IsGarbageCollectedType<Set>::value;
+};
+
+template <typename Set>
+struct IsGarbageCollectedType<ListHashSetConstIterator<Set>> {
+  static const bool value = IsGarbageCollectedType<Set>::value;
+};
+
+template <typename Set>
+struct IsGarbageCollectedType<ListHashSetReverseIterator<Set>> {
+  static const bool value = IsGarbageCollectedType<Set>::value;
+};
+
+template <typename Set>
+struct IsGarbageCollectedType<ListHashSetConstReverseIterator<Set>> {
+  static const bool value = IsGarbageCollectedType<Set>::value;
+};
+
 template <typename T, typename H>
 struct HandleHashTraits : SimpleClassHashTraits<H> {
   STATIC_ONLY(HandleHashTraits);