This was a regression from bug 133165 which I noticed while working on
bug 480888, but wished to fix in a separate patch (despite that it would
have been slightly easier to fix it in the same patch).
menulist-shrinkwrap-1 tests one of the important characteristics of the
fix: that the intrinsic size of a menulist doesn't depend on which item
is selected. It passes both with and without the patch, across
platforms.
menulist-shrinkwrap-2 tests the actual bug being fixed: that a menulist
at its intrinsic size doesn't truncate some of the items with "...". It
passes on Mac OS X with and without this patch. This patch changes it
from failing to passing on Linux. It fails on Windows XP and Windows 7
both with and without the patch, although the patch slightly reduces the
amount of text truncated on Windows 7, from "long i..." to "long it...",
although it's constant at "long i..." on Windows XP.