Re: [html-tests] Add tests for <summary>'s activation behavior (#4539)

I can confirm instability in the following contexts:

- GNU/Linux: Chromium version 57.0.2979.0 (64-bit)
- macOS: Google Chrome version 55.0.2883.95

Firefox Nightly behaves as expected on both platforms.

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.

The test is reported as flaky because a DOM with more elements (such as the one under test) 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

So this may be a bug Chromium. Probably I'm overlooking some reality of expected behavior during DOM loading, but just in case this is legitimate, I've filed a report on the Chromium issue tracker: https://bugs.chromium.org/p/chromium/issues/detail?id=681711

View on GitHub: https://github.com/w3c/web-platform-tests/pull/4539#issuecomment-272987377

Received on Monday, 16 January 2017 23:49:20 UTC