Prototype for the DWB toast in Overview

No UX spec is ready, so using some placeholder layout.
No attention to string localization since I feel that strings may
change, compared to current mocks.
Not using remaining-time API, as it is not ready.

Bug:118319143
Test: Manual
Change-Id: I50cff9099677db543e95963f058d3e89eab07d8f