Handle action modes in the IME extract mode view.

This presents action modes (such as the one for text editing) in a
less screen-consuming way in the IME extract mode layout. The submit
button is replaced by an "Edit..." button that shows the action mode
menu when clicked.

Still needs UX design and tweaking.

Change-Id: Ia7b3f3446edced0ee5a9abc5e2f0ff16f4fa3ab1