chromium/chrome/test/data/indexeddb/endure/app.html

<!DOCTYPE html>
<title>IndexedDB Offline</title>
<p>This test models the typical design of an offline-aware authoring
  application:
<ul>
<li>When "offline", a series of (fake) user events are logged into a
  store
<li>When "online", the events are played back to a (fake) server,
  draining the store
<li>When "online" a Worker synchronizes data from a (fake) remote
  source into a store in chunks, then consolidates it into another
  store
</ul>

<div id="status"></div>

<button disabled="true" id="offline">Go Offline</button>
<button disabled="true" id="online">Go Online</button>
<div id="state"></div>

<script src="app.js?cachebust"></script>