Bug 1807892 - Fix test_popup_recreate.xhtml on some platforms.

On platforms with scrollbar size > dropmarker width the popup is not
guaranteed to be bigger than the menulist after this patch and
bug 1805694 (given the "menu sizes to popup" behavior changed there).

Ensure the popup is sized to the menulist by widening the later.

MANUAL PUSH: Trivial test fix CLOSED TREE

toolkit/content/tests/chrome/test_popup_recreate.xhtml

@@ -74,7 +74,7 @@ function checkSize()
 </script>
 
 <hbox align="center" pack="center">
-  <menulist id="menulist" onpopupshown="checkSize();" onpopuphidden="recreate();">
+  <menulist id="menulist" onpopupshown="checkSize();" onpopuphidden="recreate();" style="width: 200px">
     <menupopup position="after_start">
       <menuitem label="Cat"/>
     </menupopup>