fetch-frame-resource.https.html has a long timeout to detect page load failed

Currently fetch-frame-resource.https.html uses a setTimeout of 10 seconds in order to detect that a page load failed (the failure page is considered cross-origin by some browsers, so timeout was needed). Therefore the lower bound of the test completing is 10 seconds. This seems long. Chromium's default test timeout is 6 seconds for Release builds.

The timeout was originally 1 second here, then moved to 5 seconds here and then 10 seconds here.

I could mark this as a Slow test, but am a bit reluctant and would like the test to be faster. I'm wondering if anything's changed in Mozilla's infra recently that means we might be able to explore returning the timeout to 1 second?

Start with fetch-frame-resource.https.html and inspect its 10-second setTimeout and failure-detection flow. Review the linked historical changes and Mozilla bug, then run the test while evaluating whether a shorter timeout, potentially 1 second, remains reliable. Done means the test completes faster without falsely reporting page-load failures.