Gestures: Ensure system stays awake for gesture handling

- Async broadcasts will allow the system to go back to sleep
  before the receiver handles the event.  Acquire a wake lock
  for a brief duration to allow the receiver time to receive
  (and acquire it's own wake lock if needed) the intent.

Change-Id: I0667c321178b2a27dc4bbc869b5576b98e768124