Affected versions

• 85.0a1 (2020-12-11)

Affected platforms

• Windows 10
• Ubuntu 18.04
• macOS 10.15

Steps to reproduce

1. Open any long page
2. Hit Ctrl + P
3. Hover the mouse on sheet indicator buttons

Expected result

• Tooltip should be displayed on hover for every button

Actual result

• Tooltip is displayed on hover only on the first hover action, regardless of the chosen button.

Regression range

• Not a regression, introduced once with the sheet indicator implementation

Additional notes

• Moving the cursor around while the button keeps its hover effect can trigger sporadically the tooltip

Suggested severity

• S4

Moving things to 88, cause we're mostly on Proton these days…

Backed out for failures on browser_preview_navigation.js

backout: https://hg.mozilla.org/integration/autoland/rev/56e083932986a9f99af482e9026d2a694baa4929

push: https://treeherder.mozilla.org/jobs?repo=autoland&group_state=expanded&selectedTaskRun=LD0rlgp9RP6DnEEVmzcBdA.0&revision=950e472e6ba51be30b3c273d4d78f59a355fe4b2

failure log: https://treeherder.mozilla.org/logviewer?job_id=329439168&repo=autoland&lineNumber=3534

[task 2021-02-10T00:27:06.696Z] 00:27:06 INFO - TEST-PASS | toolkit/components/printing/tests/browser_preview_navigation.js | Sheet indicator has correct value -
[task 2021-02-10T00:27:06.697Z] 00:27:06 INFO - Buffered messages logged at 00:25:27
[task 2021-02-10T00:27:06.697Z] 00:27:06 INFO - Leaving test bound testPaginatorAfterSettingsUpdate
[task 2021-02-10T00:27:06.697Z] 00:27:06 INFO - Entering test bound testTooltips
[task 2021-02-10T00:27:06.697Z] 00:27:06 INFO - withTestPage: http://example.com/browser/toolkit/components/printing/tests/longerArticle.html
[task 2021-02-10T00:27:06.697Z] 00:27:06 INFO - Buffered messages logged at 00:25:28
[task 2021-02-10T00:27:06.698Z] 00:27:06 INFO - Initial mouse move to end navigation button
[task 2021-02-10T00:27:06.699Z] 00:27:06 INFO - Waiting
[task 2021-02-10T00:27:06.699Z] 00:27:06 INFO - Buffered messages finished
[task 2021-02-10T00:27:06.699Z] 00:27:06 INFO - TEST-UNEXPECTED-FAIL | toolkit/components/printing/tests/browser_preview_navigation.js | Test timed out -
[task 2021-02-10T00:27:06.700Z] 00:27:06 INFO - GECKO(2405) | MEMORY STAT | vsize 130551198MB | residentFast 2813MB
[task 2021-02-10T00:27:06.700Z] 00:27:06 INFO - TEST-OK | toolkit/components/printing/tests/browser_preview_navigation.js | took 120097ms

Also failing: https://treeherder.mozilla.org/logviewer?job_id=329439044&repo=autoland&lineNumber=3955

Backed out for failures on browser_preview_navigation.js

• backout: https://hg.mozilla.org/integration/autoland/rev/d7b25de9e7393bba933d6c0cf77fc60c771c1abe

• push: https://treeherder.mozilla.org/jobs?repo=autoland&group_state=expanded&revision=f8061ad44728f2cf16088be807d1bf0395e25a47&selectedTaskRun=MujeXZHVRke4XU6sVjvv7Q.0

• failure log: https://treeherder.mozilla.org/logviewer?job_id=346826745&repo=autoland&lineNumber=15813

[task 2021-07-30T00:53:27.164Z] 00:53:27     INFO - TEST-PASS | toolkit/components/printing/tests/browser_preview_navigation.js | Tooltip shows correct text - 
[task 2021-07-30T00:53:27.165Z] 00:53:27     INFO - Initial mouse move to next navigation button
[task 2021-07-30T00:53:27.165Z] 00:53:27     INFO - Waiting
[task 2021-07-30T00:53:27.165Z] 00:53:27     INFO - Buffered messages finished
[task 2021-07-30T00:53:27.166Z] 00:53:27     INFO - TEST-UNEXPECTED-FAIL | toolkit/components/printing/tests/browser_preview_navigation.js | Test timed out - 
[task 2021-07-30T00:53:27.166Z] 00:53:27     INFO - GECKO(6164) | [Parent 11040, Main Thread] WARNING: Unknown color for nsLookAndFeel: file /builds/worker/checkouts/gecko/widget/windows/nsLookAndFeel.cpp:347
[task 2021-07-30T00:53:27.167Z] 00:53:27     INFO - GECKO(6164) | [Parent 11040, Main Thread] WARNING: Unknown color for nsLookAndFeel: file /builds/worker/checkouts/gecko/widget/windows/nsLookAndFeel.cpp:347
[task 2021-07-30T00:53:27.167Z] 00:53:27     INFO - GECKO(6164) | [Parent 11040, Main Thread] WARNING: Unknown color for nsLookAndFeel: file /builds/worker/checkouts/gecko/widget/windows/nsLookAndFeel.cpp:347
[task 2021-07-30T00:53:27.168Z] 00:53:27     INFO - GECKO(6164) | [Parent 11040, Main Thread] WARNING: Unknown color for nsLookAndFeel: file /builds/worker/checkouts/gecko/widget/windows/nsLookAndFeel.cpp:347
[..]
[task 2021-07-30T00:53:27.206Z] 00:53:27     INFO - TEST-OK | toolkit/components/printing/tests/browser_preview_navigation.js | took 90136ms
[task 2021-07-30T00:53:27.206Z] 00:53:27     INFO - Not taking screenshot here: see the one that was previously logged
[task 2021-07-30T00:53:27.206Z] 00:53:27     INFO - TEST-UNEXPECTED-FAIL | toolkit/components/printing/tests/browser_preview_navigation.js | Found a tab after previous test timed out: http://example.com/browser/toolkit/components/printing/tests/longerArticle.html -

https://hg.mozilla.org/mozilla-central/rev/d5c23cd282fd

Reproduced the issue on an affected Nightly build from 2020-12-11 on Win 10 x64.

Verified as fixed on Firefox Firefox 92.0.1 (20210922161155) across the following platforms: Win 10 x64, Ubuntu 20.04 and macOS 10.15.