subtask of bug 264134 Right now we have multiple ways of returning errors, often declaring a custom enum for a given method. Streamlining error handling to return a single object would simplify some code flow. For now, it will be used by MSE objects only.
<rdar://problem/118431377>
Pull request: https://github.com/WebKit/WebKit/pull/20518
Committed 270869@main (e209781a701e): <https://commits.webkit.org/270869@main> Reviewed commits have been landed. Closing PR #20518 and removing active labels.