Showing hover menu.

This menu is shown when the user hovers the mouse over the app icon for 1 sec.
Then we show the task selection (launch) menu for all apps.
It's not yet clear what should be in that menu; currently I'm just making sure it's not empty.

Bug: 20024603
Change-Id: I5d2b2a4c80d0996ee43b3e1c20ca57d95a58f1ad