sizetopopup is set to "pref" by default by the menulist XBL binding, however
when converting the binding to custom element, it did not set the attribute value
at a time that is early enough.
This patch updates nsMenuPopupFrame and nsMenuFrame so that it considers
<menulist> with unset sizetopopup attribute as equal to "pref" to avoid
the problem above.
This reftest
layout/reftests/xul/menulist-shrinkwrap-2.xul
can detect this failure.
The sizetopopup attribute is never meant to be set dynamically;
the fix here does not allow us to do so.
Differential Revision: https://phabricator.services.mozilla.com/D16410
--HG--
extra : moz-landing-system : lando