Add an insert function to our list utility class.

src/list.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 61 matching lines @@
 
   // Adds a copy of the given 'element' to the end of the list,
   // expanding the list if necessary.
   T& Add(const T& element);
 
   // Added 'count' elements with the value 'value' and returns a
   // vector that allows access to the elements.  The vector is valid
   // until the next change is made to this list.
   Vector<T> AddBlock(const T& value, int count);
 
+  // Inserts a copy of the given  element at index i in the list.  All
+  // elements formerly  at or above i  are moved up and  the length of
+  // the list increases by one.
+  T& Insert(int i, const T& element);
+
   // Removes the i'th element without deleting it even if T is a
   // pointer type; moves all elements above i "down". Returns the
   // removed element.
   T Remove(int i);
 
   // Removes the last element without deleting it even if T is a
   // pointer type. Returns the removed element.
   INLINE(T RemoveLast()) { return Remove(length_ - 1); }
 
   // Clears the list by setting the length to zero. Even if T is a
@@ skipping 22 matching lines @@
   INLINE(T* NewData(int n))  { return static_cast<T*>(P::New(n * sizeof(T))); }
   INLINE(void DeleteData(T* data))  { P::Delete(data); }
 
   DISALLOW_COPY_AND_ASSIGN(List);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_LIST_H_