Sync web-platform-tests PR 32780 into mozilla-central (this bug is closed when the sync is complete).

PR: https://github.com/web-platform-tests/wpt/pull/32780
Details from upstream follow.

Matt Wolenetz <wolenetz@chromium.org> wrote:

MSE: Fix flaky mediasource-detach failures

This change relaxes the timing expectation for 'updateend' of an
appended initialization segment meaning the media element
must already have reached HAVE_METADATA. In Chrome, the transition
to media element readyState hops threads and may occur after the
SourceBuffer's 'updateend' has been dispatched.

See the following MSE spec issue for discussion of this behavior:
https://github.com/w3c/media-source/issues/275

The test now awaits both 'updateend' and 'loadedmetadata' receipts
before issuing a load() that is expected to close the MediaSource.

This change also removes an older copy of the same test, updating
the wpt version and related test expectations.

BUG=1143720,641121

Change-Id: I87df990e3a032c6f7dadf25829093c35913c7855

Reviewed-on: https://chromium-review.googlesource.com/3450339
WPT-Export-Revision: 131a48f2f6e8ec0d113f4a09e0de5a7723a2e1db

CI Results

Ran 7 Firefox configurations based on mozilla-central, and Firefox, Chrome, and Safari on GitHub CI

Total 1 tests and 2 subtests

Status Summary

Firefox

OK : 1
FAIL: 2

Chrome

OK : 1
PASS: 2

Safari

OK : 1
PASS: 2

Links

Gecko CI (Treeherder)
GitHub PR Head
GitHub PR Base

Details

Firefox-only Failures

/media-source/mediasource-detach.html
Test media.load() before appending data will trigger MediaSource detaching from a media element.: FAIL
Test media.load() after appending data will trigger MediaSource detaching from a media element.: FAIL

New Tests That Don't Pass

/media-source/mediasource-detach.html
Test media.load() before appending data will trigger MediaSource detaching from a media element.: FAIL (Chrome: PASS, Safari: PASS)
Test media.load() after appending data will trigger MediaSource detaching from a media element.: FAIL (Chrome: PASS, Safari: PASS)

https://hg.mozilla.org/mozilla-central/rev/deb31d2f7d0a