In the Acunia test suite, in IAA.BroswerDesktopSim test, if you
continue to click on "Add New" until the new icons do not fit inside
the panel, the panel will expand to accomodate the new icons.  Some
icons will be placed below the visible area of the panel, so you won't
see them.  However, the correct behaviour is that the panel should
maintain its original size, and the icons should resize themselves so
that they will all fit inside the panel.  This way, all icons are
visible at all times.