Convert legacy 'native code' to JS-forms in dart:html

lib/html/templates/html/impl/impl_WheelEvent.darttemplate

Index: lib/html/templates/html/impl/impl_WheelEvent.darttemplate
diff --git a/lib/html/templates/html/impl/impl_WheelEvent.darttemplate b/lib/html/templates/html/impl/impl_WheelEvent.darttemplate
index a2fbc06845b4d9d4a6f9c9cf9dcaaee54fbeca30..17a95f2dc57d54378bd61b6081535cf1d8f29176 100644
--- a/lib/html/templates/html/impl/impl_WheelEvent.darttemplate
+++ b/lib/html/templates/html/impl/impl_WheelEvent.darttemplate
@@ -69,12 +69,12 @@ $if DART2JS
     return this._deltaMode;
   }
 
-  num get _deltaY() native 'return this.deltaY';
-  num get _deltaX() native 'return this.deltaX';
-  num get _wheelDelta() native 'return this.wheelDelta';
-  num get _wheelDeltaX() native 'return this.wheelDeltaX';
-  num get _detail() native 'return this.detail';
-  int get _deltaMode() native '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);
 
 $else
   int get deltaMode => 0;