Take the root-document fetch for a load of baseUrl: the unclaimed prefetch
when one is fresh, else a new fetch started now (a previous load's response is
never reused — each load validates against the server afresh). null for a URL
isShareableRootUrl rejects.
Take the root-document fetch for a load of
baseUrl: the unclaimed prefetch when one is fresh, else a new fetch started now (a previous load's response is never reused — each load validates against the server afresh).nullfor a URL isShareableRootUrl rejects.