anchor.diff:     * (The input format is the same used by the ImageData class, which can be created
      * from a canvas element.)
      */
  -  IndexedAnimation(this.width, this.height, Iterable<List<int>> rgbaFrames) {
  +  _IndexedAnimation(this.width, this.height, Iterable<List<int>> rgbaFrames) {
       for (var frame in rgbaFrames) {
         frames.add(colors.indexImage(width, height, frame));      
       }
  
positive.code: }
  
  /// An animation with a restricted palette.
  class IndexedAnimation {
    final int width;
    final int height;
    final colors = new _ColorTable();
  
negative.code:  * which can be created from a canvas element.)
   */
  Uint8List makeGif(int width, int height, List<int> rgba) {
    return new _IndexedImage(width, height, rgba).encodeGif();  
  }
  
  /**
  