anchor.diff:  
       hasCrossListing = false;
       hasPreviousContent = false;
  +
  +    _requestedSections = new _RequestedSectionRegistry()
  +      ..addRequestedSection (this);
     }
   
     /// The [setSection] method...
     void setSection (BannerSection aSection) {
       _section = aSection;
  +    _requestedSections.addRequestedSection (this);
   
       _crossListing = null;
       _previousContent = null;
  
positive.code: 
  import 'package:polymer/polymer.dart';
  
  /////////////////////////////////////////////////////////////////////
  
  /// The [BannerCourse] class...
  class BannerCourse extends JsProxy {
  
negative.code:   PreviousContentMapping get previousContent => _previousContent;
  
    PreviousContentMapping _previousContent;
  
    _RequestedSectionRegistry _requestedSections;
  
    /// The [RequestedSection] constructor...
    RequestedSection (BannerSection aSection) {
  