Fix a test to follow recent VM changes.

tests/html/unknownelement_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file
 
 library UnknownElementTest;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:html';
 
 main() {
@@ skipping 36 matching lines @@
               case 'get:x':
                 return 42;
               case 'baz':
                 return '${element.id} - ${args[0]}';
             }
             break;
           case 'bar':
             switch (name) {
               case 'get:y':
                 return map['y'];
-              case 'set:y':
+              case 'set:y=':
                 map['y'] = args[0];
                 return;
             }
             break;
         }
         throw new NoSuchMethodError(element, name, args, {});
       }
       dynamicUnknownElementDispatcher = dispatch;
 
       expect(foo.x, equals(42));
       expect(() { foo.x = 7; }, throwsNoSuchMethodError);
       expect(foo.id, equals('foo'));
       expect(() => bar.x, throwsNoSuchMethodError);
       bar.y = 11;
       expect(bar.y, equals(11));
       expect(foo.baz('hello'), equals('foo - hello'));
     });
 }