https://searchfox.org/mozilla-central/source/testing/web-platform/meta/visual-viewport/viewport-scrollbars-cause-resize.html.ini

if webrender and fission and (os == "win") and not debug: ["OK", "TIMEOUT"]

The DOM Fission team is relying on feature teams to debug and fix Fission failures in their tests. If the failure looks like a bug in Fission's DOM or IPC changes, you can send the bug back to me.

We're hoping to enable Fission for a subset of Nightly users in early Q3, so we would like WPT tests to be green for Fission by end of Q2. Whether a particular test failure actually blocks shipping Fission is up to the discretion of the feature team. You all would know better than the DOM Fission which test failures are most important.

You can enable Fission when running WPT tests locally using mach wpt --enable-fission.

Tracking WPT Fission bugs for Fission M6b (Q2)

Because this bug's Severity has not been changed from the default since it was filed, and it's Priority is P3 (Backlog,) indicating it has been triaged, the bug's Severity is being updated to S3 (normal.)

(In reply to Chris Peterson [:cpeterson] from comment #0)

https://searchfox.org/mozilla-central/source/testing/web-platform/meta/visual-viewport/viewport-scrollbars-cause-resize.html.ini

if webrender and fission and (os == "win") and not debug: ["OK", "TIMEOUT"]

The annotation was dropped in https://hg.mozilla.org/mozilla-central/rev/7a1bf4c17b25 for when a wpt sync happened. (Oddly the test doesn't have any iframe though).