am 535cc39a: am 20618b1f: am b17c8696: When phone is ringing, power button should only mute the ringer, not hang up.

Merge commit '535cc39aa7e6b13ffd53160c242361f8462ebc33'

* commit '535cc39aa7e6b13ffd53160c242361f8462ebc33':
  When phone is ringing, power button should only mute the ringer, not hang up.