anchor.diff:  
     List<int> sublist(int start, [int end]) {
       if (end == null) end = length;
  -    return Lists.getRange(this, start, end, <int>[]);
  +    return _Lists.getRange(this, start, end, <int>[]);
     }
   
     Map<int, int> asMap() =>
  
positive.code: 
    List<int> sublist(int start, [int end]) {
      if (end == null) end = length;
      return Lists.getRange(this, start, end, <int>[]);
    }
  
    Map<int, int> asMap() =>
  
negative.code: import 'dart:_js_helper' show Creates, JavaScriptIndexingBehavior, JSName, Null, Returns;
  import 'dart:_foreign_helper' show JS;
  
  // TODO: migrate to ListMixin.
  class _Lists {
  
    /**
     * Returns the index in the array [a] of the given [element], starting
     * the search at index [startIndex] to [endIndex] (exclusive).
     * Returns -1 if [element] is not found.
     */
    static int indexOf(List a,
                       Object element,
                       int startIndex,
                       int endIndex) {
      if (startIndex >= a.length) {
        return -1;
      }
      if (startIndex < 0) {
        startIndex = 0;
      }
      for (int i = startIndex; i < endIndex; i++) {
        if (a[i] == element) {
          return i;
        }
      }
      return -1;
    }
  
    /**
     * Returns the last index in the array [a] of the given [element], starting
     * the search at index [startIndex] to 0.
     * Returns -1 if [element] is not found.
     */
    static int lastIndexOf(List a, Object element, int startIndex) {
      if (startIndex < 0) {
        return -1;
      }
      if (startIndex >= a.length) {
        startIndex = a.length - 1;
      }
      for (int i = startIndex; i >= 0; i--) {
        if (a[i] == element) {
          return i;
        }
      }
      return -1;
    }
  
    /**
     * Returns a sub list copy of this list, from [start] to
     * [end] ([end] not inclusive).
     * Returns an empty list if [length] is 0.
     * It is an error if indices are not valid for the list, or
     * if [end] is before [start].
     */
    static List getRange(List a, int start, int end, List accumulator) {
      if (start < 0) throw new RangeError.value(start);
      if (end < start) throw new RangeError.value(end);
      if (end > a.length) throw new RangeError.value(end);
      for (int i = start; i < end; i++) {
        accumulator.add(a[i]);
      }
      return accumulator;
    }
  }
  /**
   * Describes endianness to be used when accessing a sequence of bytes.
   */
  