Reset keyguard/bouncer on "return to call".

+ Add callback, to be invoked when EmergencyButton is clicked when
inside a call.
+ Route callback to the KeyguardViewMediator, to invoke
resetStateLocked() to reset the bouncer.

Bug: 18977746
Change-Id: I4733ccfb6809c4610184a33a28ba38ecf255231f
8 files changed