Performance.observe with both entryTypes and buffered

[jgraham]

Description

In this case the spec says to throw, but not all implementations currently throw.

This is an issue with observed webcompat breakage.

Specification

https://w3c.github.io/performance-timeline/#dom-performanceobserver-observe

Additional Signals

https://bugzilla.mozilla.org/show_bug.cgi?id=1915589
https://issues.chromium.org/issues/40694412

[wpt-interop]

Thank you for proposing Performance.observe with both entryTypes and buffered for inclusion in Interop 2025.

We are pleased to let you know that this proposal was accepted as part of the Web Compat focus area. You can follow the progress of this focus area on the Interop 2025 dashboard.

For an overview of our process, see proposal selection. Thank you for contributing to Interop 2025!

Posted on behalf of the Interop team.