Merge "MediaRouter2: Add missing synchronized(sRouterLock) block" into rvc-dev am: 5aacc569c7 am: 7c4fbecb8d am: e6afe3dcb5

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

Change-Id: I1611a7719b1767b8a08727b5b1db679eda277208