In sp15, I did a google search for "macbook pro dissection" in a new window, and command clicked on the link for MacDailyNews article at:
http://macdailynews.com/index.php/weblog/comments/9585/
And this same thing happened, the background tab focused, and became the active tab, with the 1.5 tab problem. I can't duplicate it, however, as OW isn't blocking the ads on that site, perhaps?
-Craig