The needed change is to rely on history as source of truth for location instead of window.location.
btw, This makes possible to test state syncing utils integration using createMemoryHistory()
One issue was discovered after this change:
When switching from context to discover url was incorrect. history.location inside state syncing utils didn't get the last update. This happened, because history instance created in discover wasn't used in context app and when all listeners unsubscribed from it - it stopped receiving location updates. To fix this I just reused one history instance in discover, context and their kbnUrlTracker
3b1d0e0c6b