Merge "MediaRouter2: Add missing synchronized(sRouterLock) block" into rvc-dev am: 5aacc569c7 am: 7c4fbecb8d

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

Change-Id: I7695f4fbade4abf0ee22890c632e63fb9ebcf2a3