Two-way-databinding doesn't work for win-toolbar-command attributes

Two-way-databinding doesn't seem to work on toolbar command attributes. [I made a fiddle.](https://jsfiddle.net/silkimen/pr7f96cm/1/)
I'm using the toolbar directive with toolbar commands configured as "toggle" buttons. The "selected" attribute is bound to a boolean on the scope. But changing the buttons selection state doesn't update my boolean.
