Rumble events may be received for controllers that are no longer present or attached
so they should be dropped instead of being forwarded to JS for handling.
Pepper SDK and NaCl in general is EOL for Chrome, although still supported for Chrome Apps.
This means that the Pepper Gamepad API was never updated with rumble support so in order
to add rumble support, rumble messages from Gamestream have to be forwarded to JavaScript
and handled with gamepad.vibrationActuator.playEffect().
Side note, Chrome limits the duration of playEffect to 5 seconds and requesting more than
that causes the vibration request to be rejected.
