Deprecating old DOM event APIs.

tests/html/streams_test.dart

 library streams_test;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:async';
 import 'dart:html';
 
 class StreamHelper {
   var _a;
   StreamHelper() {
     _a = new TextInputElement();
     document.body.append(_a);
   }
 
   Element get element => _a;
   Stream<Event> get stream => _a.onFocus;
 
   // Causes an event on a to be fired.
   void pulse() {
     var event = new Event('focus');
-    _a.$dom_dispatchEvent(event);
+    _a.dispatchEvent(event);
   }
 }
 
 main() {
   useHtmlConfiguration();
 
   test('simple', () {
     var helper = new StreamHelper();
 
     var callCount = 0;
@@ skipping 132 matching lines @@
       ++callCountOne;
     });
     helper.pulse();
     expect(callCountOne, 1);
 
     subscription.onData(null);
     helper.pulse();
     expect(callCountOne, 1);
   });
 }