chrome/browser/resources/sync_internals/events.html

<style>
#sync-events-table,
#sync-events-table th,
#sync-events-table td {
  border: 1px black solid;
}

#sync-events-table {
  width: 100%;
}

#sync-events > tr {
  vertical-align: top;
}
</style>

<table id="sync-events-table">
  <thead>
    <th>Time</th>
    <th>Submodule</th>
    <th>Event</th>
    <th>Details</th>
  </thead>
  <tbody id="sync-events">
  </tbody>
</table>

<script>
(function() {
function makeLogEntryNode(entry) {
  var timeNode = document.createElement('td');
  timeNode.innerText = entry.date;

  var submoduleNode = document.createElement('td');
  submoduleNode.innerText = entry.submodule;

  var eventNode = document.createElement('td');
  eventNode.innerText = entry.event;

  var details = document.createElement('pre');
  details.innerText = JSON.stringify(entry.details, null, 2);
  var detailsNode = document.createElement('td');
  detailsNode.appendChild(details);

  var node = document.createElement('tr');
  node.appendChild(timeNode);
  node.appendChild(submoduleNode);
  node.appendChild(eventNode);
  node.appendChild(detailsNode);

  return node;
}

var syncEvents = document.getElementById('sync-events');

var entries = chrome.sync.log.entries;
for (var i = 0; i < entries.length; ++i) {
  syncEvents.appendChild(makeLogEntryNode(entries[i]));
}

chrome.sync.log.addEventListener('append', function(event) {
  syncEvents.appendChild(makeLogEntryNode(event.detail));
});
})();
</script>