Affected versions:

• Nightly 91.0a1

Affected platforms:

• Ubuntu 20.04.2 LTS

Unaffected platforms:

• Windows 10x64
• macOS 10.15

Steps to reproduce:

1. Launch Firefox.
2. Go to Customize toolbar (Hamburger menu → More tools → Customize toolbar).
3. Select Dark theme from the list.
4. Select Alpenglow theme.

Expected result:
Customization footer buttons are clearly visible.

Actual result:
Customization footer buttons appear only after 1-2 seconds after the Alpenglow theme is selected.

Regression range:

• pushlog: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=feaff6bddf649886164bfb5897dbf33b8789d930&tochange=0e6c67113ca7dba2de8101156993c563da62a3a1
• possible regressor: Bug 1707872

Additional notes
Screen cast attached to illustrate the issue.
The issue reproduces only when switching from Dark to Alpenglow theme.

Hi Emilio,

It seems that mozregression pointed out Bug 1717872 for causing this regression.

Can you please take a look?

Thanks!

That way we guarantee they are processed before display.

Backed out for multiple failures.

• backout: https://hg.mozilla.org/integration/autoland/rev/c561b38fa930e8432277cbc5b0cf806cffce313a

• push: https://treeherder.mozilla.org/jobs?repo=autoland&revision=b6b225d4a81c111616923a2047c6a1c2c5d2fffe&group_state=expanded

• failure logs:

  • TEST-UNEXPECTED-FAIL | LeakSanitizer | leak at CountingMalloc, ICUReporter::Alloc, icu_69::Collator::makeInstance, icu_69::Collator::createInstance
  • TEST-UNEXPECTED-FAIL | leakcheck | default 703701 bytes leaked (AnimationTimeline, AsyncFreeSnowWhite, BackstagePass, CacheObserver, CharacterData, ...)
  • TEST-UNEXPECTED-FAIL | layout/style/test/test_mq_any_hover_and_any_pointer.html | Doesn't match (any-pointer: none)

This allows us to remove the timeout (which was there for these prefs)
and makes the code a bit more explicit.

Unconditionally making all tests wait for rAF causes some timing changes
which cause some tests to time out / fail, see:

https://treeherder.mozilla.org/jobs?repo=try&revision=3aef4c168c6ab7d762dd360f49d4f56dff686c03

So this only does it when changing the prefs that care about it. Fix
some tests that were relying on the timeout to get this green.

Depends on D119023

Backed out for causing build bustages

Backout link: https://hg.mozilla.org/integration/autoland/rev/a752ceb19cf2f406e082dd76b0b038088a149dba

Push with failures

Failure log

@emilio

could this failure be from this bug?

Otherwise after the previous change we might get some reftest failures
like this in noqr platforms if the snapshot is taken too soon:

https://treeherder.mozilla.org/jobs?repo=try&revision=5452076b8278fdb514e8c3bc10486b0c74917eb0

This patch fixes it.

Backed out for causing Reftest failures.

Backout link: https://hg.mozilla.org/integration/autoland/rev/a10e7c2df383a4363d3bdd512851a0b198ccd8e1

Push with failures: https://treeherder.mozilla.org/jobs?repo=autoland&selectedTaskRun=chAyS-qBRk2gtJ_oMp6EKg.0&resultStatus=testfailed%2Cbusted%2Cexception&revision=babc4fdcd08c8ccb4ee11c93da0791eac2239de2&searchStr=OS%2CX%2C10.15%2CWebRender%2Cdebug%2CReftests%2Ctest-macosx1015-64-qr%2Fdebug-reftest-e10s%2CR4

Failure log:

• https://treeherder.mozilla.org/jobs?repo=autoland&resultStatus=testfailed%2Cbusted%2Cexception&selectedTaskRun=chAyS-qBRk2gtJ_oMp6EKg.0
• https://treeherder.mozilla.org/logviewer?job_id=345206824&repo=autoland&lineNumber=6199
• https://treeherder.mozilla.org/logviewer?job_id=345202797&repo=autoland&lineNumber=4390

https://hg.mozilla.org/mozilla-central/rev/9d579691527b
https://hg.mozilla.org/mozilla-central/rev/92e9abe2b2ad
https://hg.mozilla.org/mozilla-central/rev/12f268910571
https://hg.mozilla.org/mozilla-central/rev/9ac290ec5884

Managed to reproduce the issue on Nightly 2021-06-30 using Ubuntu 18.04 x64.
Retested everything on Firefox 92.0b2 and Nightly 93.0a1 using the same os. The issue is not reproducing anymore.