Update WebKit idl files after chrome roll

tools/dom/templates/html/impl/impl_WheelEvent.darttemplate

Index: tools/dom/templates/html/impl/impl_WheelEvent.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_WheelEvent.darttemplate b/tools/dom/templates/html/impl/impl_WheelEvent.darttemplate
index 12088fe86b02964f4aca6343bef7b5b7002a5d4b..1ce11692f5e9be0576c67d7fd5125b38da2ed3d8 100644
--- a/tools/dom/templates/html/impl/impl_WheelEvent.darttemplate
+++ b/tools/dom/templates/html/impl/impl_WheelEvent.darttemplate
@@ -134,20 +134,11 @@ $if DART2JS
         'deltaX is not supported');
   }
 
-  int get deltaMode {
-    if (JS('bool', '!!#.deltaMode', this)) {
-      // If not available then we're poly-filling and doing pixel scroll.
-      return 0;
-    }
-    return this._deltaMode;
-  }
-
   num get _deltaY => JS('num', '#.deltaY', this);
   num get _deltaX => JS('num', '#.deltaX', this);
   num get _wheelDelta => JS('num', '#.wheelDelta', this);
   num get _wheelDeltaX => JS('num', '#.wheelDeltaX', this);
   num get _detail => JS('num', '#.detail', this);
-  int get _deltaMode => JS('int', '#.deltaMode', this);
 
   bool get _hasInitMouseScrollEvent =>
       JS('bool', '!!(#.initMouseScrollEvent)', this);