Style MobileContext properly

It should show up below the main toolbar. This is a follow up to
Id8cc4b07905f777f667f36cbcc65e821847142d5. The styling will need to be
changed in the future if we want MobileContext to be rendered properly
outside of MW.

Change-Id: I13fa3dc4f85fd3413c5939c118d54f11f1e98076