Force FormLayout children to shrink with the layout (#11154)

Force FormLayout children to shrink with the layout (#11154)

The <table> used by the FormLayout doesn't reduce its size if any child
component has locked its own size (which is the case with e.g. Table and
some other components doing explicit pixel calculations). To work around
this, we need to detect the situation, force the <table> to reduce its
width by temporarily assigning explicit widths to the cells and then
remove the forced size after all children have adjusted.

Change-Id: Iacef62979acf24c869a5cbeb82efb0c1e537ec95