Fixing up WheelEvent to follow W3C standards and work on all platforms.

lib/html/templates/html/interface/interface_WheelEvent.darttemplate

Index: lib/html/templates/html/interface/interface_WheelEvent.darttemplate
diff --git a/lib/html/templates/html/interface/interface_CanvasElement.darttemplate b/lib/html/templates/html/interface/interface_WheelEvent.darttemplate
similarity index 61%
copy from lib/html/templates/html/interface/interface_CanvasElement.darttemplate
copy to lib/html/templates/html/interface/interface_WheelEvent.darttemplate
index ca44aefd9dd087e66b47e16969e644ab826498ea..d887078b73cae5dfd71b804aa99fb4cd1a9f520c 100644
--- a/lib/html/templates/html/interface/interface_CanvasElement.darttemplate
+++ b/lib/html/templates/html/interface/interface_WheelEvent.darttemplate
@@ -2,10 +2,16 @@
 // 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.
 
-// WARNING: Do not edit - generated code.
-
 $!COMMENT
 abstract class $ID$EXTENDS {
 $!MEMBERS
-  final CanvasRenderingContext2D context2d;
+
+  /** @domName WheelEvent.deltaX */
+  num get deltaX;
+
+  /** @domName WheelEvent.deltaY */
+  num get deltaY;
+
+  /** @domName WheelEvent.deltaMode */
+  int get deltaMode;
 }