Build ID 20210407212527
User Agent Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:89.0) Gecko/20100101 Firefox/89.0

When I test Bug 1700101, I found the bug.
The sub-view won't load.

Steps to reproduce:

1. Put Text Encoding toolbutton in Overflow Menu.
2. Open data:text/html;Shift_JIS,Other than UTF-8:%E3%81%82<a href="https://www.google.com" style="float:right;padding-right:50px;">Go to Google</a>
3. Click Overflow Menu button.
4. Click Text Encoding to open sub-view.
5. Click < button at the top-left corner of the menu
6. Repeat step 4 and step 5.

Actual results:
Suddenly, the sub-view is corrupted.
Once a problem occurs, the sub-view will no longer be visible.

Profiler:
https://share.firefox.dev/3t1l1Nc
https://share.firefox.dev/2Q6ufJc

Even if WebRender is disabled, the problem is reproduced.

profiler:
https://share.firefox.dev/31YR7NH
https://share.firefox.dev/3fQRWjG

AND Even if HWA is disabled, the problem is occurred.

Profiler:
https://share.firefox.dev/2OweCKX

AND Even if HWA and Webrender is disabled(i.e, Basic compositor), the problem is occurred.

Profiler:
https://share.firefox.dev/3wC3EVl

if proton is disabled, this problem doesn't seem to be occurring.

If you pref on proton is there a meaningful regression range?

(In reply to Timothy Nikkel (:tnikkel) from comment #5)

If you pref on proton is there a meaningful regression range?

Attempt to find the regression window with the following prefs (See about:support in Comment 3)
user_pref("browser.proton.enabled", true);
user_pref("layers.acceleration.disabled", true);
user_pref("gfx.webrender.force-disabled", true);
user_pref("gfx.webrender.software", false);
user_pref("gfx.webrender.software.unaccelerated-widget.allow", false);

Regression Window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=850595648fbff342e535b9f30ef09e1e0c0580a5&tochange=ae0f3f0e993a5fd012a845f06c8a4ce3f48c0164

Before Bug 1702474, Bug 1703569 appears.
After landing Bug 1702474, this glitch appears.

(The problem occurs after about 10 repetitions of Step 6 in Comment 0.)

STR

1. Put Library button in nav bar
2. Click the button
3. Click Boookmarks >
4. Click < button
5. Repeat step 3, 4

Actual Results:
Transition to sub-view stops without completing. See attached screenshot.

Given what you know now from the regression range, does this seem like a graphics bug?

(In reply to Timothy Nikkel (:tnikkel) from comment #9)

Given what you know now from the regression range, does this seem like a graphics bug?

Actually, no idea.
First I thought Graphic WebRender as Bug 1700101.
But, This is reproduced in Basic Compositor, then I remove WebRender.

And, invisible rectangle(black rectangle in profiler's screenshot)

Nightly browser hangs for long period. No mouse/keyboards response for long period.

Profiler:
https://share.firefox.dev/3t8ckRi

Bug 1704927 was landed on autoland, but the hang is still reproduced on latest autoland...

Jim, could this be prioritized and triaged wrt 89? Thanks

Are there any errors reported in the browser console when this happens?

(In reply to Matt Woodrow (:mattwoodrow) from comment #15)

Are there any errors reported in the browser console when this happens?

Several warning messages and an error messagein Browser Console:

browser.ui.interaction.pinned_overflow-menu - Unknown scalar.  6

TypeError: can't access property "descriptionHeightWorkaround", mainPanelView is undefined PanelMultiView.jsm:1258:9
    handleEvent resource:///modules/PanelMultiView.jsm:1258

The try build of Bug 1709998 fixed this too.

Bug 1709998 fixed this on Nightly90.0a1(20210511093339).

However, I can still reproduce the issue on 89.0b10.