Make ListIterator throw if the underlying list's length changes.

sdk/lib/collection_dev/list.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart.collection.dev;
 
 /**
  * Class implementing the read-operations on [List].
  *
  * Implements all read-only operations, except [:operator[]:] and [:length:],
@@ skipping 255 matching lines @@
     throw new UnsupportedError(
         "Cannot insert range in an unmodifiable list");
   }
 }
 
 /**
  * Iterates over a [List] in growing index order.
  */
 class ListIterator<E> implements Iterator<E> {
   final List<E> _list;
+  final int _initialLength;
   int _position;
   E _current;
 
-  ListIterator(List<E> list) : _list = list, _position = -1;
+  ListIterator(List<E> list)
+      : _list = list, _position = -1, _initialLength = list.length;
 
   bool moveNext() {
+    if (_list.length != _initialLength) {
+      throw new ConcurrentModificationError(_list);
+    }
     int nextPosition = _position + 1;
     if (nextPosition < _list.length) {
       _current = _list[nextPosition];
       _position = nextPosition;
       return true;
     }
     _position = _list.length;
     _current = null;
     return false;
   }
@@ skipping 226 matching lines @@
       throw new ConcurrentModificationError(list);
     }
     if (_index <= _start) return false;
     _index -= 1;
     _current = _list[_index];
     return true;
   }
 
   E get current => _current;
 }