For Bug 1601052 I'm implementing a workaround where I have to wait for both TabSelect and the focus change, to be sure we touch the urlbar at the right time after a tab switch.
This happens more often when switching tabs repeatedly, the TabSelect event normally fires after _adjustFocusAfterTabSwitch, but sometimes it fires before it, so we get a TabSelect and then the focus changes to/from the urlbar.
Having a reliable timeline would help with implementing features, and it's unclear if this may be a cause for intermittent failures.