Getting better speed from adjusting rows in a DockableToolBar
I have one little suggestion with regard to style. It is much better to invert your conditions to have the simpler code run first when it involves yielding control. It also helps you avoid excessive indentation. 

var child:DockableToolBar = DockableToolBar(row.getChildAt(k));

//Skip the rest of the row if we can't move the first child up.
if (prevRowW + child.measuredWidth &gt;= toolbar.width) {
    break;
}

//Move child.
child.parent.removeChild(child);
prevRow.addChild(child);
prevRowW += child.measuredWidth;
--k;