New option and changes
Add switchLastActiveTab option
Change on tab create to scroll only if tab activated
Change active on mouseup instead of mousedown, seems cleaner for switchLastActiveTab option and drag event
Change _onBrowserTabUpdated workflow, seems more effiecient this way.
Remove webNavigation.onCompleted event already manage by tabs.onUpdated event with status completed
The name of the new option switchLastActiveTab
can be change.
The idea comes from what you have done for Tree Style tab.
I've just noticed that I modified some indentation (sorry), I'll make a rollback for this later.