Adding event type getter to EventStreamProvider.

tests/html/wheelevent_test.dart

Index: tests/html/wheelevent_test.dart
diff --git a/tests/html/wheelevent_test.dart b/tests/html/wheelevent_test.dart
index f5b7e2d5c94f195b0511543dd3e7cc8e371bbfa2..6de15285ad320bae6d8c92d82e01e271e5d11d44 100644
--- a/tests/html/wheelevent_test.dart
+++ b/tests/html/wheelevent_test.dart
@@ -12,30 +12,16 @@ main() {
 
   useHtmlConfiguration();
 
-  var userAgent = window.navigator.userAgent;
-
-  // Lame platform-dependent check to validate that our assumptions about
-  // which event is being used is correct.
-  var wheelEvent = 'wheel';
-  if (userAgent.contains("Opera", 0)) {
-    wheelEvent = 'mousewheel';
-  } else if (userAgent.contains("MSIE", 0)) {
-    wheelEvent = 'mousewheel';
-  } else if (userAgent.contains('Firefox')) {
-    // FF appears to have recently added support for wheel.
-    wheelEvent = 'wheel';
-  } else if (userAgent.contains('WebKit', 0)) {
-    wheelEvent = 'mousewheel';
-  }
-
   test('wheelEvent', () {
     var element = new DivElement();
+    var eventType = Element.mouseWheelEvent.getEventType(element);
+
     element.onMouseWheel.listen(expectAsync1((e) {
       expect(e.screenX, 100);
       expect(e.deltaX, 0);
       expect(e.deltaY, 240);
     }));
-    var event = new WheelEvent(wheelEvent,
+    var event = new WheelEvent(eventType,
       deltaX: 0,
       deltaY: 240,
       screenX: 100);
@@ -44,12 +30,14 @@ main() {
 
   test('wheelEvent Stream', () {
     var element = new DivElement();
+    var eventType = Element.mouseWheelEvent.getEventType(element);
+
     element.onMouseWheel.listen(expectAsync1((e) {
       expect(e.screenX, 100);
       expect(e.deltaX, 0);
       expect(e.deltaY, 240);
     }));
-    var event = new WheelEvent(wheelEvent,
+    var event = new WheelEvent(eventType,
       deltaX: 0,
       deltaY: 240,
       screenX: 100);