Judging by
https://github.com/rackt/react-router/blob/master/docs/API.md#children-1
and a few inspections in the code, as well as tests, the `children`
prop injected into routes can only ever be a single React Element
object.
This allows us to easily get the active route of a child (if there is
an active route) by querying the `children`’s route prop.
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