I ran into a case where I was setting minHeight=∞ and then calling
layout() with that constraint, which is all kinds of bad. To try to
catch this earlier, this patch now provides a way to catch constraints
that are requiring infinite values.
We don't _always_ check this because there are valid uses for
BoxConstraints.biggest, e.g. as an additionalConstraint.
New RenderAligningShiftedBox abstract class for render boxes with
"alignment", which as of now is:
- RenderPositionedBox
- RenderConstrainedOverflowBox (ex RenderOverflowBox)
- RenderSizedOverflowBox
- RenderFractionallySizedOverflowBox (ex RenderFractionallySizedBox)
(The respective widgets are Align, OverflowBox, SizedOverflowBox, and
FractionallySizedBox. They haven't been renamed.)
Also I added some toString details.
