ActivityManagerService: Fix heavy games kill during incoming call

Force heavy apps penalisation only to large "cached" apps. Donot
include "previous" app in this category. This ensures large apps
are not killed during special incoming alerts like incall, sms.

Change-Id: I51b4a238415efad63ef36f7e0cd056823a72a47d
SystemUI: disable statusbar time refresh when screen off

When screen is off, don't refresh the status bar to save power.
When screen is on, refresh immediately for user experience.

Change-Id: Ie250e20bab57c096a16886680a53263c635bf6f4

Conflicts:
	packages/SystemUI/src/com/android/systemui/statusbar/policy/Clock.java