The test is invalid, it assumes that the `SourceBuffer.updating` attribute will be false when `loadedmetadata` is fired. This assumption would be okay in WK1 or if the SourceBufferPrivate runs in the content process as all is done synchronously in this case. But should this test run in the GPU Process, that assumption will always be incorrect and calling SourceBuffer.append() while `SourceBuffer.updating == true` will throw
<rdar://problem/107162814>
Pull request: https://github.com/WebKit/WebKit/pull/11898
Committed 262069@main (99cbb993489c): <https://commits.webkit.org/262069@main> Reviewed commits have been landed. Closing PR #11898 and removing active labels.