Bug 1039001 - [B2G] [Camera] Unplugging device while taking a timed picture with low battery will not stop the picture being taken.

These are the different battery levels:
'healthy', 'low', 'verylow', 'critical', 'shutdown'

I think we should let the timer take a picture at least in 'low' and 'verylow' states. Low means 15% battery and verylow 10%