anchor.diff:  
     final bool enableNative;
   
  -  final bool isPlatformLibrary;
  +  final bool isBuiltinLibrary;
   
     @override
     final Uri uri;
  
positive.code:       : enclosingScope = scope,
          library = library,
          enableNative = library.loader.target.enableNative(library),
          isPlatformLibrary = library.uri.scheme == 'dart',
          needsImplicitSuperInitializer =
              coreTypes.objectClass != classBuilder?.cls,
          typePromoter = _typeInferrer.typePromoter,
  
negative.code:           return new UnresolvedAccessor(this, n, token);
          }
          return new ThisPropertyAccessor(this, token, n, null, null);
        } else if (isBuiltinLibrary &&
            name == "main" &&
            member?.name == "_getMainClosure") {
          // TODO(ahe): https://github.com/dart-lang/sdk/issues/28989
          return new KernelNullLiteral()..fileOffset = offsetForToken(token);
        } else {
  