Allow holders of SYSTEM_ALERT_WINDOW permission to start
activities from background

Bug: 130222474
Test: manual, seeing log:
mkarpinski@mkarpinski2:~/android/qt-dev$ adb logcat -b system | grep "allowed because SYSTEM"
04-26 15:55:41.761  1283  3067 W ActivityTaskManager: Background activity start for com.facebook.orca allowed because SYSTEM_ALERT_WINDOW permission is granted.
Change-Id: I7d0a2ae7fde9b1f7f96a4936d872397a7e07ce0e
3 files changed