Let the second pass phantom callbacks run in a separate task on the foreground thread.

src/list.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_LIST_H_
 #define V8_LIST_H_
 
+#include <algorithm>
+
 #include "src/checks.h"
 #include "src/utils.h"
 
 namespace v8 {
 namespace internal {
 
 template<typename T> class Vector;
 
 // ----------------------------------------------------------------------------
 // The list is a template for very light-weight lists. We are not
@@ skipping 112 matching lines @@
   // Clears the list by setting the length to zero. Even if T is a
   // pointer type, clearing the list doesn't delete the entries.
   INLINE(void Clear());
 
   // Drops all but the first 'pos' elements from the list.
   INLINE(void Rewind(int pos));
 
   // Drop the last 'count' elements from the list.
   INLINE(void RewindBy(int count)) { Rewind(length_ - count); }
 
+  // Swaps the contents of the two lists.
+  INLINE(void Swap(List<T, AllocationPolicy>* list));
+
   // Halve the capacity if fill level is less than a quarter.
   INLINE(void Trim(AllocationPolicy allocator = AllocationPolicy()));
 
   bool Contains(const T& elm) const;
   int CountOccurrences(const T& elm, int start, int end) const;
 
   // Iterate through all list entries, starting at index 0.
   void Iterate(void (*callback)(T* x));
   template<class Visitor>
   void Iterate(Visitor* visitor);
@@ skipping 66 matching lines @@
 template <typename T, class P>
 int SortedListBSearch(const List<T>& list, P cmp);
 template <typename T>
 int SortedListBSearch(const List<T>& list, T elem);
 
 
 } }  // namespace v8::internal
 
 
 #endif  // V8_LIST_H_