This implements the step of choosing a browsing context with
FindWithName, which should be equivalent to calling
nsIDocShellTreeItem.findItemWithName passing null for 'aRequestor' and
'aOriginalRequestor' and false for 'aSkipTabGroup'.
Differential Revision: https://phabricator.services.mozilla.com/D15190
--HG--
extra : moz-landing-system : lando