Always show the overflow button

As with native action bars.

Change-Id: Ibb577bc3bcbf7b51b3b6d1fee9e72cb9390fabf9
Update the overflow touch background color from blue to gray

Use the parent theme's system touch background.

Change-Id: Icf6099cbe07f5f2b71afbf3823d1fddceca999c4