Make WheelEvent.delta{X,Y} return num, not int.

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_WheelEvent.darttemplate b/lib/html/templates/html/interface/interface_WheelEvent.darttemplate
index d623c4c0fe8122f5abf4a17c37485562d0ab9360..1966c897183539f277ff26647a760da38d2bdb6b 100644
--- a/lib/html/templates/html/interface/interface_WheelEvent.darttemplate
+++ b/lib/html/templates/html/interface/interface_WheelEvent.darttemplate
@@ -6,6 +6,12 @@ $!COMMENT
 abstract class $ID$EXTENDS {
 $!MEMBERS
 
+  /** @domName WheelEvent.deltaX */
+  abstract num get deltaX;
+
+  /** @domName WheelEvent.deltaY */
+  abstract num get deltaY;
+
   /** @domName WheelEvent.deltaMode */
-  int get deltaMode;
+  abstract int get deltaMode;
 }