[ActivityManager] Reduce report wrong anr activity

Symptom:
Report ANR on wrong activity.

Reproduce steps:
 (All launchMode, taskAffinity are default and
  without additional intent flag)
 Case 1:
  1.Launch activity A from launcher.
  2.Activity A starts B activity.
  3.Press home key.
  4.Launch activity A from launcher (B is top).
  5.Press back key twice to finish B and A,
    A sleep 10s in onResume.
  6.ANR will report on launcher.

 Case 2:
  1.Launch activity A from launcher.
  2.Press home key.
  3.Kill process of A.
  4.Launch activity A from launcher.
  5.A sleep 10s in onResume, press back key immediately.
  6.ANR will report on launcher.

Possible root cause:
Focused activity will not be updated every time when activity
resumed. (the condition to call setFocusedActivityLocked)

Case 1:
Launcher was stopped and not waitingVisible due to launcher
is not the previous one, then getWaitingHistoryRecordLocked
has no chance to correct the real ANR activity.

Case 2:
Due to process of next activity is died, bring existed
task will not set mResumedActivity (it will be set when its
process is started), so when assigning waitingVisible from
processStoppingActivitiesLocked, the return value of
allResumedActivitiesVisible will be true even there is no
mResumedActivity. That results set waitingVisible to false
to previous activity (e.g. launcher), then also cannot
correct ANR target as case 1.

Change-Id: I0b24f46a8fab266382ebc6e2ed84ebeca9358768