Comment 8 for bug 514541

FYI, I am the developer that plays devil's advocate. With that in mind...

"Predictability" is something that is determined based on a point of reference. You may call 'changing icons' unpredictable. Others however might look at as 'always showing the current document's icon' and thus, it is predictable.

Thus we have a third option: leave it as is and it will have a predictable icon.