Previously the router just stored a `root_found` boolean after it picked a
route. But on re-render it would just always return false from `should_render`
if this was true. This just aborted routing after a future resolved (or
anything else that triggered a re-render).
Now we store the matching ScopeId and check that against our routes in a
re-render so we actually do re-render the matching route.
Dave Rolsky
81c094ed29