Adding event type getter to EventStreamProvider.

tools/dom/src/EventStreamProvider.dart

Index: tools/dom/src/EventStreamProvider.dart
diff --git a/tools/dom/src/EventStreamProvider.dart b/tools/dom/src/EventStreamProvider.dart
index 776d6026eb45c8c5377458de96f3e6914cc88ad4..2dd9560c27e2d10628761999f8d0f19a6b689963 100644
--- a/tools/dom/src/EventStreamProvider.dart
+++ b/tools/dom/src/EventStreamProvider.dart
@@ -134,6 +134,17 @@ class EventStreamProvider<T extends Event> {
   Stream<T> forTarget(EventTarget e, {bool useCapture: false}) {
     return new _EventStream(e, _eventType, useCapture);
   }
+
+  /**
+   * Gets the type of the event which this would listen for on the specified
+   * event target.
+   *
+   * The target is necessary because some browsers may use different event names
+   * for the same purpose and the target allows differentiating browser support.
+   */
+  String getEventType(EventTarget target) {
+    return _eventType;
+  }
 }
 
 /**
@@ -149,4 +160,8 @@ class _CustomEventStreamProvider<T extends Event>
   Stream<T> forTarget(EventTarget e, {bool useCapture: false}) {
     return new _EventStream(e, _eventTypeGetter(e), useCapture);
   }
+
+  String getEventType(EventTarget target) {
+    return _eventTypeGetter(target);
+  }
 }