Emil Ghitta, QA [:emilghitta] Reporter
	Description • 6 years ago

[Affected versions]:
Firefox 62.0a1 (BuildId:20180515100038).
Firefox 61.0b4 (BuildId:20180510160705).
	
[Affected platforms]:
Windows 10 64bit.
macOS 10.13.3.
Ubuntu 16.04 64bit.

[Steps to reproduce]:
1.Launch Firefox.
2.Access the https://www.youtube.com webpage.
3.Enable the Accessibility features.
4.Click the "Pick accessible object from the page" button.
5.Hover over webpage elements while scrolling through the webpage. 

[Expected result]:
A transparent overlay is successfully displayed over the hovered elements and no performance issues are encountered.

[Actual result]:
Firefox freezes while scrolling through the webpage elements and the only way to restart the browser is to kill the process.

After doing this several times, some IPCError-browser | ShutDownKill crash reports were generated:
- 7fe3ee7a-6bf4-44cc-9e0c-ad7180180515
- 60e9138a-cba4-4716-b145-33f460180515

[Regression range]:
I don't think that this is a regression.

[Additional information]:
For further information regarding this issue please observe the attached screencast.
I also generate a dump file: https://drive.google.com/open?id=1MRGpN58jz7b5vn5BCTfgxU8OJEq96st1
I managed to reproduce this issue on websites like: YouTube or Imgur.

	Yura Zenevich [:yzen] (please use "needinfo")
	Comment 1 • 6 years ago

Hi Emil, I noticed similar lag on YouTube and the HTLM inspector, is that something you observe on your side?

	Emil Ghitta, QA [:emilghitta] Reporter
	Comment 2 • 6 years ago

Hi Yura, 

Unfortunately, I can't reproduce this lag with the html inspector.

	Yura Zenevich [:yzen] (please use "needinfo")
	Comment 3 • 6 years ago

Thanks, 

FYI we have this message when starting the tool:

"Accessibility features are deactivated by default because they negatively impact performance. Consider turning off accessibility features before using other Developer Tools panels."

It is still worth further investigation though, in case we can improve certain things. Best results I've seen were related to not on-the-spot highlighting (Chrome does that) so it could be one option in the future.

	James Teh [:Jamie]
	Comment 4 • 6 years ago

(In reply to Yura Zenevich [:yzen] from comment #1)
> Hi Emil, I noticed similar lag on YouTube and the HTLM inspector, is that
> something you observe on your side?

Yura, did you have accessibility enabled (even without the a11y inspector) when testing? Wondering whether this is a general a11y issue. Certainly, we have bug 1395536 concerning a11y perf with Youtube.

	Yura Zenevich [:yzen] (please use "needinfo")
	Comment 5 • 6 years ago

(In reply to James Teh [:Jamie] from comment #4)
> (In reply to Yura Zenevich [:yzen] from comment #1)
> > Hi Emil, I noticed similar lag on YouTube and the HTLM inspector, is that
> > something you observe on your side?
> 
> Yura, did you have accessibility enabled (even without the a11y inspector)
> when testing? Wondering whether this is a general a11y issue. Certainly, we
> have bug 1395536 concerning a11y perf with Youtube.

I don't believe I had, I don't think I tried it on Windows either. I will look at this bug this week though.