embedding/components/windowwatcher/nsWindowWatcher.cpp is full of the use of 0 for pointer values instead of nullptr. We should clean this up. Good first bug!
Oh, I just noticed this problem, too. Bug 1130096 is going to clean up the style of this file, so it'll probably bitrot any patch you may have.
Let me know if you have any questions about this. If you aren't actually working on this feel free to just unassign yourself. ;)