User Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36

Steps to reproduce:

The issue seems to be reproducible from 71.0 Firefox version (tested on Windows 10).

1. Open any page sample with contenteditable element. You can use https://codepen.io/jacekbogdanski/pen/QWwNOoV
2. Open FF search bar using CTRL + F keyboard combination.
3. Focus contenteditable element.
4. Start navigating using keyboard arrow keys.

Keyboard navigation works fine until you open a search bar. The issue didn't occur on Firefox 70.

Actual results:

It is possible to use all keys even if the search bar of Firefox is opened.

Expected results:

It is not able to move a caret.

I can reproduce the issue on Nightly63.0a1 Windows10 as well as Firefox71.

STR:

1. Open any page sample with contenteditable element. You can use https://codepen.io/jacekbogdanski/pen/QWwNOoV
2. Focus contenteditable element by mouse click.
3. Open Findbar using CTRL + F keyboard combination.
   --- The caret can be moved to left and right with the left/right arrow keys. OK
4. Focus contenteditable element again.
5. Start navigating using keyboard arrow keys.
   --- It is not able to move a caret. BUG

Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=5b303cb0a0a39e2bd4a6fea53535fe8e1d829b97&tochange=e33c3e14ee40f88d1775952e309dc2a617eb97f7

[Tracking Requested - why for this release]:Mail compose window Yahoo! Japan is also affected if Findbar is opened

Also affected to https://mail.yahoo.co.jp/ compose window

Too late for 71.

Hi Mike, can you please take a look at this while Neil is on PTO?

I can't reproduce this bug at all.

I can still reproduce the issue with STR Comment#1 on Nightly73.0a1(20191222215627) Windows10.

Also affected to https://ckeditor.com/latest/samples/index.html

Tentatively assigning to Neil because he said planned to investigate these findbar regressions next week, unless Mike makes progress before then.

Tracking for Fission dogfooding (M5)

I can reproduce this bug in both Fission and non-Fission mode. Caret navigation is broken even after closing the Findbar.

We don't need to track this bug for Fission since non-Fission mode is also broken.

Depends on D58990

https://hg.mozilla.org/mozilla-central/rev/9a8af38a964f
https://hg.mozilla.org/mozilla-central/rev/3f585af46d39

I can reproduce the issue on Nightly74.0a1(20200120094216) Windows10.
And I verified that the issue was fixed in Nightly74.0a1(20200121093246).

Please nominate this for Beta approval when you get a chance.

Comment on attachment 9119183 [details]
Bug 1603020, send state update messages to all child actors, r=mikedeboer

Beta/Release Uplift Approval Request

• User impact if declined: After opening the findbar, typing/moving the caret does not work in some contenteditable fields
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky):
• String changes made/needed: None

Comment on attachment 9119183 [details]
Bug 1603020, send state update messages to all child actors, r=mikedeboer

regression fix, approved for 73.0b11

https://hg.mozilla.org/releases/mozilla-beta/rev/be4754a40d8e
https://hg.mozilla.org/releases/mozilla-beta/rev/d7efce529200

Reproduced the initial issue using Release version 72.0.2.
Verified - Fixed in latest Beta 73.0b11 (Build id: 20200128001646) using Windows 10.