1.屏蔽FallbackHome启动弹窗

问题场景：Android系统定制中去除锁屏KeyGuard服务之后，在系统开机进入Launcher之前，会有手机正在启动中弹窗，这部分主要涉及Settings中的FallbackHome，解决方案如下：

2. 延长开机动画

代码路径： framework/services/core/java/com/android/server/wm/WindowManagerService.java

//注释掉关闭开机动画这段代码
 /* if (!mBootAnimationStopped) {
      Trace.asyncTraceBegin(TRACE_TAG_WINDOW_MANAGER, "Stop bootanim", 0);
      // stop boot animation
      // formerly we would just kill the process, but we now ask it to exit so it
      // can choose where to stop the animation.
      SystemProperties.set("service.bootanim.exit", "1");
      mBootAnimationStopped = true;
  }

  if (!mForceDisplayEnabled && !checkBootAnimationCompleteLocked()) {
      if (DEBUG_BOOT) Slog.i(TAG_WM, "performEnableScreen: Waiting for anim complete");
      return;
  }

  try {
      IBinder surfaceFlinger &