If you create a vbox in mxml and do not specify a height the
vbox scales to the height of the contents.
If you set a vbox height in mxml to 0 and then later want to
have that vbox scale to the height of the contents within it what
do you do? I can't seem to find anything in actionscript to get the
auto height scaling then you get with setting the height to nothing
myvbox.height = x doesn't work. Null doesn't work.
myvbox.percentHeight = various thing doesn't work.