Add rotate suggestion button to gestural nav.

Fixes: 128942468
Test: 1. In fully gestural mode, rotation/back button is moved to the
bottom left corner and keyboard button is moved to the bottom right.
When the keyboard is up, rotation button does not show. The rotation
button in this setting has an oval background that matches the home
handle color.
2. In 2-button and 3-button mode, the rotation button stays the same.
Screenshot: https://screenshot.googleplex.com/or2GbOzmZTX

Change-Id: I32f2f11d33bf6881a67770679db2118917d2123b