在9.0 设备中，由于定制的设备没有音量+和音量-按键，所以通过手动选择recovery选择界面的模式时，就不能选择进入哪种模式，这时就需要进入recovery的时候
默认进入恢复出厂设置模式
首选看下recovery.cpp相关源码
路径:bootable\recovery\recovery.cpp
首选看下main()方法
int main(int argc, char **argv) {
// We don't have logcat yet under recovery; so we'll print error on screen and
// log to stdout (which is redirected to recovery.log) as we used to do.
android::base::InitLogging(argv, &UiLogger);
// Take last pmsg contents and rewrite it to the current pmsg s