Adding supported checks for touch event.

sdk/lib/html/dartium/html_dartium.dart

Index: sdk/lib/html/dartium/html_dartium.dart
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index 2c7dd638ec7e9a08421cb56160575b2a0aed8e26..fa5fdf1c25cbddf1150a306711c85463e80c2621 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -24541,6 +24541,14 @@ class TouchEvent extends UIEvent {
   @DocsEditable
   void $dom_initTouchEvent(TouchList touches, TouchList targetTouches, TouchList changedTouches, String type, Window view, int screenX, int screenY, int clientX, int clientY, bool ctrlKey, bool altKey, bool shiftKey, bool metaKey) native "TouchEvent_initTouchEvent_Callback";
 
+
+  /// Checks if this type is supported on the current platform.
+  static bool get supported {
+    // TODO: add equivalent 'ontouchstart' check for Dartium.
+    // Basically, this is a fairly common check and it'd be great if it did not
+    // throw exceptions.
+    return Event._isTypeSupported('TouchEvent');
+  }
 }
 // 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