Comment 6 for bug 1300382

If, in the above HTML example, I change "input" to "keyup" as the name of the event, I can reproduce the issue on my N7 (and pressing a hardware button such as volume up or volume down "flushes the state").

So it seems that those websites, instead of listening to the "input" event, only listen to key events. However they work fine on e.g. chrome on android, so there must be something chrome is doing that triggers a key event when the OSK is used to input text, or something similar.