一個電話打出去的流程 (代碼流程)

1. TwelveKeyDialer.java, onKeyUp()
2. TwelveKeyDialer.java, placeCall()
3. OutgoingCallBroadcaster.java, onCreate()
    sendOrderedBroadcast(broadcastIntent, PERMISSION,
                new OutgoingCallReceiver(), null, Activity.RESULT_OK, number, null);
4. OutgoingCallBroadcaster.java, OutgoingCallReceiver
    doReceive -> context.startActivity(newIntent);
5. InCallScreen.java, onCreate/onNewIntent
6. InCallScreen.java, placeCall
7. PhoneUtils.java, placeCall
8. GSMPhone.java, dial
9. GsmCallTracker.java, dial
10. RIL.java, dial
      RILRequest rr = RILRequest.obtain(RIL_REQUEST_DIAL, result);
      ...
      send(rr);