Bug 250553 Classic <menulist> should not see command events from its popup's <scrollbarbutton>s r=doron sr=roc

xpfe/global/resources/content/bindings/scrollbar.xml

@@ -19,6 +19,7 @@
       <handler event="click" action="event.preventBubble();"/>
       <handler event="dblclick" action="event.preventBubble();"/>
       <handler event="mousemove" action="event.preventBubble();"/>
+      <handler event="command" action="event.preventBubble();"/>
       <handler event="contextmenu" action="event.preventBubble();"/>
     </handlers>
   </binding>