It would be great to have the "Work offline" feature exposed in the devtools as a button/toggle. Together with bug #1204115 (work offline feature affecting local connections) this would make a great addition to the tools for developers working with service workers/progressive webapps, and a very handy feature Chrome devtools-parity-wise: https://developers.google.com/web/fundamentals/getting-started/codelabs/offline/#test_the_app I'd imagine the top-right shortcut button strip would be a great place for this toggle (especially since those could be enabled/disabled in the devtools settings panel, so developers working with service workers could enable this, while for others this could remain turned off to reduce clutter).

The new Responsive Design Mode adds network throttling (but not yet offline). Once we have per-tab offline support, adding an offline option would be natural.