anchor.diff:  
     Set<Class> _unneededNativeClasses;
   
  +  List<StubMethod> _jsInteropIsChecks = [];
  +
     /// Classes that have been allocated during a profile run.
     ///
     /// These classes should not be soft-deferred.
  
positive.code:     // a method in the case where there exist multiple JavaScript classes
      // that conflict on whether the member is a getter or a method.
      Class interceptorClass = _classes[_commonElements.jsJavaScriptObjectClass];
      Set<String> stubNames = {};
      librariesMap
          .forEach((LibraryEntity library, List<ClassEntity> classElements, _) {
  
negative.code:       // Currently we generate duplicates if a class is implemented by multiple
        // js-interop classes.
        typeTests.forEachProperty(_sorter, (js.Name name, js.Node code) {
          _jsInteropIsChecks.add(_buildStubMethod(name, code));
        });
      } else {
        for (Field field in instanceFields) {
  