Merge "MediaRouter2: Add missing synchronized(sRouterLock) block" into rvc-dev am: 5aacc569 am: 84a06dbe

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/11782206

Change-Id: Ie207ecf724cb6feacddeb834fbd06529e90a8920