CAF接收器：cast.framework.system.SystemState。STARTING_IN_BACKGROUND？

Question

有人知道系统状态STARTING_IN_BACKGROUND和STOPPING_IN_BACKGROUND的用途吗？ documentation不太清楚：

STARTING_IN_BACKGROUND: Application is starting but it is in background.
STOPPING_IN_BACKGROUND: Application is stopping but it is in background.

是否可以在后台启动CAF接收器应用程序？

我使用过的查询参数google_cast_bg=true是否与之相关？

//www.gstatic.com/cast/sdk/libs/caf_receiver/v3/cast_receiver_framework.js?google_cast_bg=true