MediaRouterService binds services when necessary
MediaRouterService maintained bindings to provider services
once those are established.
With this CL, it only binds services when there is a non-empty
discovery preference set by a foreground app or an app is casting.
This change may break output switcher, which enables transfer media
of background apps.
To alleviate that MediaRouter2Manager#startScan and #stopScan are added
so that system UI can force the service bind to the services and find
remote devices to cast.
Bug: 169575701
Bug: 172920557
Test: manually and CTS
Change-Id: I4a47fdb1c9fe05a04d26950485833c9cbfb91a69
(cherry picked from commit 9f889ca4e62044900004cb7ce4e85415d2b019e2)
(cherry picked from commit 602b168f99b00c037191234a85190d845680aa64)
13 files changed
