Merge "MediaRouter2: Add missing synchronized(sRouterLock) block" into rvc-dev am: 5aacc569c7 am: 84a06dbe0b am: 03e02b09b7

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

Change-Id: Ifdb16ca446973ab1e7d2aacb0d6f4610d56ac736