[Webkit-unassigned] [Bug 167263] LayoutTest media/modern-media-controls/media-controller/media-controller-auto-hide.html is flaky

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=167263

--- Comment #3 from Antoine Quint <graouts at apple.com> ---
OK, I think I understand what makes this test flaky.

First, the test makes the assumption that the auto-hide timer can only be started as a result of the "play" event firing… but it turns out that when "loadedmetadata" fires, media.paused can be set to "false", and ControlsVisibilitySupport which governs when the controls bar is set to have fadesWhileIdle = true, uses both "loadedmetadata" and "play" as triggers provided media.paused = "false". So that's the first issue, since we could potentially wait enough time until we'd assume the auto-hide timer started to make our 200ms and 300ms timers off-base enough.

Second, while the system is under stress (in my case I have a full WK build and running the test with GuardMalloc), there might be a significant delta between the moment the same event is handled within the media controls code and when it's handled in the test. Locally, I can see something around 85ms as the delay. This would cause another significant delay to make the 200ms and 300ms timers off-base.

So this test is definitely flaky by nature, and all of the other auto-hide tests, many of which are showing flakiness, suffer from the same design flaw. I'll need to think of a better, more robust way to write those tests.

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