Remove files that have already been ported or do not need to be ported.

client/html/src/_ListIterators.dart

-// Copyright (c) 2011, 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.
-
-// Iterator for lists with fixed size.
-class _FixedSizeListIterator<T> extends _VariableSizeListIterator<T> {
-  _FixedSizeListIterator(List<T> list)
-      : super(list),
-        _length = list.length;
-
-  bool hasNext() => _length > _pos;
-
-  final int _length;  // Cache list length for faster access.
-}
-
-// Iterator for lists with variable size.
-class _VariableSizeListIterator<T> implements Iterator<T> {
-  _VariableSizeListIterator(List<T> list)
-      : _list = list,
-        _pos = 0;
-
-  bool hasNext() => _list.length > _pos;
-
-  T next() {
-    if (!hasNext()) {
-      throw const NoMoreElementsException();
-    }
-    return _list[_pos++];
-  }
-
-  final List<T> _list;
-  int _pos;
-}