Chrome Version       : Chromium	57.0.2979.0 (Developer Build) (64-bit)
                       Revision	5a213ac08a1ea69d04c2fc9e4f21fe53c109ff52-refs/heads/master@{#442975}
OS Version: Ubuntu 16.04.1 LTS
URLs (if applicable) : https://bl.ocks.org/jugglinmike/e5f13288f675836e2cca8aec8d2a2424 https://bl.ocks.org/jugglinmike/661f878cc5448a86072c40c3d3336a93
Other browsers tested:
     Safari:
    Firefox: OK -- 50.1.0; 53.0a1 (2017-01-12) (64-bit)
         IE:

What steps will reproduce the problem?
(1) During initial page load trigger a `click` event on a `<summary>` element
    nested within a `<details>` element

What is the expected result?

The user agent adds an attribute named `open` to the `<details>` element.

What happens instead?

Nothing

Please provide any additional information below. Attach a screenshot if
possible.

It looks like Chromium does not update the `<details>` element when a `click`
event is triggered during initial page rendering:

```html
<details>
  <summary id="d">Summary</summary>
  Content
</details>

<script>document.getElementById('d').click();</script>
```

Demo: https://bl.ocks.org/jugglinmike/e5f13288f675836e2cca8aec8d2a2424

Note that the `click` event is still created and propagated as expected.

A DOM with more elements occasionally prompts Chromium to honor the click.

Demo: https://bl.ocks.org/jugglinmike/661f878cc5448a86072c40c3d3336a93

The flakyness may be more prominent when the document is loaded directly (in
other words, not from within an `<iframe>`):
https://bl.ocks.org/jugglinmike/raw/661f878cc5448a86072c40c3d3336a93