anchor.diff:  
     // private methods that modify map state
   
  -  _resetView(center, zoom, preserveMapOffset, afterZoomAnim) {
  +  _resetView(center, zoom, [preserveMapOffset=false, afterZoomAnim=false]) {
   
       var zoomChanged = (this._zoom != zoom);
   
  
positive.code: import 'dart:html';
  import 'dart:math' as math;
  
  class Options {
    CRS crs;
    bool fadeAnimation;
    bool trackResize = true;
    bool markerZoomAnimation;
  }
  
  class Map {
    Options options;
  
    List _handlers;
  
  
negative.code: 
    // map initialization methods
  
    var _container;
  
    _initContainer(id) {
      var container = this._container = L.DomUtil.get(id);
  
      if (!container) {
        throw new Exception('Map container not found.');
      } else if (container._leaflet) {
        throw new Exception('Map container is already initialized.');
      }
  
      container._leaflet = true;
  