Disable KeyBindingManager on right Alt keydown.

This fixes issue #8666.
I used console.log to print out the keydown events and noticed that the delay between Ctrl and Alt keys are 1 ms for AltGr key, but more than 100 ms for pressing Ctrl and Alt keys together. So I chose 30 ms, giving enough time for AltGr key down on slow machines. I don't think that we can control the interval from unit test to verify the ideal interval.