It's allowed, but the buffered option is ignored. This is what Blink does [1], what WebKit does [2]. (Both code blocks are inside the else branch of if `has entryTypes`) The web-platform-test in this change was originally copied from buffered-flag-after-timeout.any.js and modified. [1] https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/timing/performance_observer.cc;l=264-273;drc=78780a188fe3c79fe815b170f4ea33e62ceb6e04 [2] https://searchfox.org/wubkat/rev/6c800745251d53d6486443d63b35828504446c5d/Source/WebCore/page/PerformanceObserver.cpp#90-100 [3] https://searchfox.org/mozilla-central/rev/e24277e20c492b4a785b4488af02cca062ec7c2c/testing/web-platform/tests/performance-timeline/buffered-flag-after-timeout.any.js Differential Revision: https://phabricator.services.mozilla.com/D233447
