Tracing HeapListHashSet<> iterators.

third_party/WebKit/Source/wtf/ListHashSet.h

Index: third_party/WebKit/Source/wtf/ListHashSet.h
diff --git a/third_party/WebKit/Source/wtf/ListHashSet.h b/third_party/WebKit/Source/wtf/ListHashSet.h
index 1c98df110f5a925a06b40833f13a92fc0a6f979d..7295dc934c282ab1b56eebbb97d5059f56a67883 100644
--- a/third_party/WebKit/Source/wtf/ListHashSet.h
+++ b/third_party/WebKit/Source/wtf/ListHashSet.h
@@ -538,6 +538,11 @@ class ListHashSetIterator {
 
   operator const_iterator() const { return m_iterator; }
 
+  template <typename VisitorDispatcher>
+  void trace(VisitorDispatcher visitor) {
+    m_iterator.trace(visitor);
+  }
+
  private:
   Node* getNode() { return m_iterator.getNode(); }
 
@@ -595,6 +600,12 @@ class ListHashSetConstIterator {
     return m_position != other.m_position;
   }
 
+  template <typename VisitorDispatcher>
+  void trace(VisitorDispatcher visitor) {
+    visitor->trace(*m_set);
+    visitor->trace(m_position);
+  }
+
  private:
   Node* getNode() { return m_position; }
 
@@ -649,6 +660,11 @@ class ListHashSetReverseIterator {
 
   operator const_reverse_iterator() const { return m_iterator; }
 
+  template <typename VisitorDispatcher>
+  void trace(VisitorDispatcher visitor) {
+    m_iterator.trace(visitor);

[haraken, 2016/12/20 02:53:05]

Just to confirm: This iterator is just pointing to a Node of ListHashSet and not
pointing to anything middle in a backing storage, right?

[sof, 2016/12/20 06:37:08]

Yes, the nodes in this list are separately allocated, which the backing store
then keeps pointers to, for faster access than the linked view. The iterator
refers to the current node + the ListHashSet<> itself for when it needs to get
at the head/tail of the list.

+  }
+
  private:
   Node* getNode() { return m_iterator.node(); }
 
@@ -706,6 +722,12 @@ class ListHashSetConstReverseIterator {
     return m_position != other.m_position;
   }
 
+  template <typename VisitorDispatcher>
+  void trace(VisitorDispatcher visitor) {
+    visitor->trace(*m_set);
+    visitor->trace(m_position);
+  }
+
  private:
   Node* getNode() { return m_position; }