anchor.diff:     */
     void replaceSelections(Iterable<String> replacement, {String select}) {
       callArgs('replaceSelections', select != null ?
  -        [new JsObject.jsify(replacement), select] :
  -        [new JsObject.jsify(replacement)]);
  +        [jsify(replacement), select] :
  +        [jsify(replacement)]);
     }
   
     /**
  
positive.code:       head = new Position.fromProxy(obj['head']),
        anchor = new Position.fromProxy(obj['anchor']);
  
    operator==(other) => other is Span &&
        head == other.head && anchor == other.anchor;
  
  
negative.code:    * options as [setSelection].
     */
    void setSelections(Iterable<Span> ranges, {int primary, Map options}) {
      callArgs('setSelections', [new JsArray.from(ranges.map((Span range) =>
          range.toProxy())), primary, options]);
    }
  
    /**
  