This means that:
- the RSS preview tab opens in the same container in which the opener
tab was open (without need for extra permissions);
- the RSS preview tab appears right next to the tab from which it was
opened, not at the end of the tab bar; and
- if the user closes the tab without switching tabs between opening and
closing the tab, Firefox activates the previous tab (i.e. from which
the RSS preview was opened), not the next one.
