Show dialog if top app is killed by lmk

Bug: 65488249
Fixes: 65488249
Test: run an app, then kill from command line like so
      adb shell "kill \$(pidof app)"

Change-Id: I7c259542723a9659c52e4571071ec5809693816d
Merged-In: I7c259542723a9659c52e4571071ec5809693816d