[Affected platforms]:
Platforms: Windows

[Steps to reproduce]

1. Enable High Contrast on Windows.
2. Launch the Firefox browser and trigger the Protocol handler modal like opening a zoom meeting link and Hover over the Checkbox
3. Trigger the Add Bookmark modal and hover over the Tags arrow.

[Expected result]
The Checkbox from the protocol handler and the Tag arrow from the Bookmark modal should change their state when the user hovers over them.

[Actual result]
The Checkbox will not change its state when hovering over and when the user checks it and then hovers over it disappears.
The Tag arrow is not displayed unless the user Hovers over it.
Please note that after a user changes focus to a different app like taking a screenshot the tag arrow becomes visible and the user can click it without issues.

Depends on D115020

Depends on D115021

Comment on attachment 9222503 [details]
Bug 1710852 - Fix button focus styles in HCM common.css usage r?Gijs

Revision D115422 was moved to bug 1712617. Setting attachment 9222503 [details] to obsolete.

Backed out along with Bug 1712617 for failures on browser_parsable_css.js

backout: https://hg.mozilla.org/integration/autoland/rev/fb43b717746227a41b394af16bb32a2cbc1af924

push: https://treeherder.mozilla.org/jobs?repo=autoland&group_state=expanded&revision=1631131e806014dde79be6e36115453f0746788d&selectedTaskRun=Bf4PvoJVRcOiH8IjA8RWiw.0

failure log: https://treeherder.mozilla.org/logviewer?job_id=340774353&repo=autoland&lineNumber=3226

[task 2021-05-25T20:56:55.057Z] 20:56:55 INFO - Console message: [JavaScript Warning: "Unknown property ‘-moz-context-properties’. Declaration dropped." {file: "jar:file:///builds/worker/workspace/build/application/firefox/browser/features/formautofill@mozilla.org.xpi!/chrome/content/formautofill.css?always-parse-css-0.005509428696064966" line: 43}]
[task 2021-05-25T20:56:55.058Z] 20:56:55 INFO - Buffered messages finished
[task 2021-05-25T20:56:55.059Z] 20:56:55 INFO - TEST-UNEXPECTED-FAIL | browser/base/content/test/static/browser_parsable_css.js | Got error message for chrome://global/skin/in-content/common.css: Selector expected. Ruleset ignored due to bad selector. -
[task 2021-05-25T20:56:55.060Z] 20:56:55 INFO - Stack trace:
[task 2021-05-25T20:56:55.060Z] 20:56:55 INFO - chrome://mochikit/content/browser-test.js:test_ok:1334
[task 2021-05-25T20:56:55.061Z] 20:56:55 INFO - chrome://mochitests/content/browser/browser/base/content/test/static/browser_parsable_css.js:messageIsCSSError:247
[task 2021-05-25T20:56:55.061Z] 20:56:55 INFO - chrome://mochitests/content/browser/browser/base/content/test/static/browser_parsable_css.js:checkAllTheCSS:468
[task 2021-05-25T20:56:55.062Z] 20:56:55 INFO - Ignored error "Unknown pseudo-class or pseudo-element ‘-moz-has-dir-attr’. Ruleset ignored due to bad selector." on resource://gre-resources/html.css because of whitelist item {"sourceName":"/\b(contenteditable|EditorOverride|svg|forms|html|mathml|ua)\.css$/i","errorMessage":"/Unknown pseudo-class.-moz-/i","isFromDevTools":false,"used":true}
[task 2021-05-25T20:56:55.063Z] 20:56:55 INFO - Ignored error "Unknown pseudo-class or pseudo-element ‘-moz-dir-attr-rtl’. Ruleset ignored due to bad selector." on resource://gre-resources/html.css because of whitelist item {"sourceName":"/\b(contenteditable|EditorOverride|svg|forms|html|mathml|ua)\.css$/i","errorMessage":"/Unknown pseudo-class.-moz-/i","isFromDevTools":false,"used":true}
[task 2021-05-25T20:56:55.064Z] 20:56:55 INFO - Ignored error "Unknown pseudo-class or pseudo-element ‘-moz-dir-attr-ltr’. Ruleset ignored due to bad selector." on resource://gre-resources/html.css because of whitelist item {"sourceName":"/\b(contenteditable|EditorOverride|svg|forms|html|mathml|ua)\.css$/i","errorMessage":"/Unknown pseudo-class.-moz-/i","isFromDevTools":false,"used":true}
[task 2021-05-25T20:56:55.067Z] 20:56:55 INFO - Ignored error "Unknown pseudo-class or pseudo-element ‘-moz-dir-attr-like-auto’. Ruleset ignored due to bad selector." on resource://gre-resources/html.css because of whitelist item {"sourceName":"/\b(contenteditable|EditorOverride|svg|forms|html|mathml|ua)\.css$/i","errorMessage":"/Unknown pseudo-class.-moz-/i","isFromDevTools":false,"used":true}

https://hg.mozilla.org/mozilla-central/rev/b93e9eba0829
https://hg.mozilla.org/mozilla-central/rev/bc7e20913288

This issue is Verified as fixed in our latest Beta 90.0b4 .

This issue Still occurs in Firefox 89.