The spec language specifies 'Set maxScopeString to "/", followed by the
strings in XXXX’s path (including empty strings), separated from each
other by "/"': That is, adjacent components are separated by a '/', but
the last component does not get a trailing '/'.
This resulted in the generated scope string ending with '//' in some
cases, incorrectly tripping the 'Service-Worker-Allowed' security check
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