I have also encountered something like this. Using google-chrome on unity-2d (4.12.0-0ubuntu1), frequently when I go to alt-tab from it to either gnome-terminal or emacs, the intended application just flashes in the switcher. I haven't determined exactly what conditions for alt-tabbing away from chrome which triggers this, but it definitely occurs several times an hour. If I can determine exact steps to reproduce I will do so, but thus far I haven't found anything that always reproduces the problem.
I will investigate if it happens regularly after the browser pops up a notification as that sounds related to the previous bug.
I have also encountered something like this. Using google-chrome on unity-2d (4.12.0-0ubuntu1), frequently when I go to alt-tab from it to either gnome-terminal or emacs, the intended application just flashes in the switcher. I haven't determined exactly what conditions for alt-tabbing away from chrome which triggers this, but it definitely occurs several times an hour. If I can determine exact steps to reproduce I will do so, but thus far I haven't found anything that always reproduces the problem.
I will investigate if it happens regularly after the browser pops up a notification as that sounds related to the previous bug.