Since about:newtab now runs in the privileged content process, SessionStore
will attempt restore the tab's content whenever we perform a process switch.
This causes the tab's content area to be focused. We will add a condition to
prevent focusing on the tab's content area.
This patch also focuses on the URL bar first before opening a new tab to avoid
flickering.
MozReview-Commit-ID: FRKR6pReiZz