Introduce per-display active client. Also, deactivate previous client when window loses focus so that connection can be restarted on next focus gain. Test: Manually using the steps in bug. Bug: 131619304 Change-Id: Iefad3f018ef0cc1b3729af4a140afa1b52139ce0 Merged-In: Iefad3f018ef0cc1b3729af4a140afa1b52139ce0