Display browser preferences/flags used at wpt.fyi

[guest271314]

Navigate to the page https://wpt.fyi/interop/offscreen-canvas/the-offscreen-canvas/2d.getcontext.exists.html?diff&filter=ADC&run_id=358480001&run_id=343560004.

Hover mouse over

6a3a002

which displays, in pertinent part

test Using prefs in /testing/profiles/; some experimental features enabled

Is /testing/profiles/ publicly stored and accessible?

Implement a means to display the preferences/flags launch settings for the browsers used at the wpt.fyi page.

[gsnedders]

Is /testing/profiles/ publicly stored and accessible?

it's https://searchfox.org/mozilla-central/source/testing/profiles in mozilla-central

[guest271314]

@gsnedders Where are the preferences used?

[guest271314]

Are the launch preferenced used exclusively at https://searchfox.org/mozilla-central/source/testing/profiles/reftest/user.js ?

[guest271314]

@gsnedders Can you confirm that gfx.offscreen.enabled preference is set to true for the version of Firefox used for the linked OffscreenCanvas test at #1648 (comment)?

[gsnedders]

I can't see it being set to true?

Are the launch preferenced used exclusively at https://searchfox.org/mozilla-central/source/testing/profiles/reftest/user.js ?

No. Look at profiles.json, and then the web-platform-tests field within there. The pref files are applied in the order they appear in that list (i.e., base/user.js, common/user.js, etc.).

[guest271314]

user_pref("media.block-autoplay-until-in-foreground", false); is set twice in web-platform/user.js. There is at least one more duplicate entry in unittest-required/user.js.

This issue is a feature request to display the preferences set corresponding to the browser linked at the test result page.