Tests tabbed pane max tab element width calculation.

Bug 75005
measuredWidths = [20,50,70], totalWidth = 150, maxWidth = 70.
measuredWidths = [20,50,80], totalWidth = 150, maxWidth = 80.
measuredWidths = [20,50,90], totalWidth = 150, maxWidth = 80.
measuredWidths = [20,90,90], totalWidth = 150, maxWidth = 65.
measuredWidths = [70,80,90], totalWidth = 150, maxWidth = 50.