Bugzilla

This is a regression.  Regression range:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=3ff8ac39b364436a63b387f445899a7db0d3ddd8&tochange=fa3677b2a1e568a0831c7f0a1507cd9972bdd420
In that range, I suspect this would've been fallout from Bug 1718012 ("Call UpdateSizesBeforeReflow only for resize reflow cases...")

hiro, maybe you can take a look here?

To be extra clear, here are the STR:
1. Visit `about:debugging#/runtime/this-firefox`
2. Click "Load Temporary Add-on"
3. Choose a locally-saved copy of the attached .zip
4. Click the extension icon on your toolbar.[i]
5. If the popup stays blank for more than a few seconds[ii], click the extension button again to close it, and then click it again to open it.
6. After https://www.iana.org loads in the popup, try to scroll the page all the way to the end (e.g. with mousewheel, or by clicking and dragging scrollbar).

EXPECTED RESULTS:
When you reach the bottom (i.e. you can't scroll anymore), the scrollbar thumb should also reach the bottom of its scrollbar track.

ACTUAL RESULTS:
When you reach the bottom (i.e. you can't scroll anymore), the **scrollbar thumb has not yet reached the bottom of its scrollbar track**. It's as if the scrollbar track thinks there's more scrollable overflow than there actually is.



Notes:
[i] As hinted at in the beginning of comment 2: in recent Nightlies, the extension icon may be hidden in an "unified extensions" menu.
[ii] In older nightlies (until ~April 2022), the popup usually just stays blank for me the first time that I open it. But if I close & reopen it again, it populates as-expected.

This is a regression.  Regression range:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=3ff8ac39b364436a63b387f445899a7db0d3ddd8&tochange=fa3677b2a1e568a0831c7f0a1507cd9972bdd420
In that range, I suspect this would've been fallout from Bug 1718012 ("Call UpdateSizesBeforeReflow only for resize reflow cases...")

hiro, maybe you can take a look here?

To be extra clear, here are the STR:
1. Visit `about:debugging#/runtime/this-firefox`
2. Click "Load Temporary Add-on"
3. Choose a locally-saved copy of the reporter's attached `popup.zip` minimal extension.
4. Click the extension icon that appears on your toolbar.[i]
5. If the popup stays blank for more than a few seconds[ii], click the extension button again to close it, and then click it again to open it.
6. After https://www.iana.org loads in the popup, try to scroll the page all the way to the end (e.g. with mousewheel, or by clicking and dragging scrollbar).

EXPECTED RESULTS:
When you reach the bottom (i.e. you can't scroll anymore), the scrollbar thumb should also reach the bottom of its scrollbar track.

ACTUAL RESULTS:
When you reach the bottom (i.e. you can't scroll anymore), the **scrollbar thumb has not yet reached the bottom of its scrollbar track**. It's as if the scrollbar track thinks there's more scrollable overflow than there actually is.



Notes:
[i] As hinted at in the beginning of comment 2: in recent Nightlies, the extension icon may be hidden in an "unified extensions" menu.
[ii] In older nightlies (until ~April 2022), the popup usually just stays blank for me the first time that I open it. But if I close & reopen it again, it populates as-expected.

This is a regression.  Regression range:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=3ff8ac39b364436a63b387f445899a7db0d3ddd8&tochange=fa3677b2a1e568a0831c7f0a1507cd9972bdd420
In that range, I suspect this would've been fallout from Bug 1718012 ("Call UpdateSizesBeforeReflow only for resize reflow cases...")

hiro, maybe you can take a look here?

To be extra clear, here are the STR:
1. Visit `about:debugging#/runtime/this-firefox`
2. Click "Load Temporary Add-on"
3. Choose a locally-saved copy of the reporter's attached `popup.zip` minimal extension.
4. Click the extension icon that appears on your toolbar.[i]
5. If the popup stays blank for more than a few seconds[ii], click the extension button again to close it, and then click it again to open it.
6. After https://www.iana.org loads in the popup, try to scroll the page all the way to the end (e.g. with mousewheel, or by clicking and dragging scrollbar).

EXPECTED RESULTS:
When you reach the bottom (i.e. you can't scroll anymore), the scrollbar thumb should also reach the bottom of its scrollbar track.

ACTUAL RESULTS:
When you reach the bottom (i.e. you can't scroll anymore), the **scrollbar thumb has not yet reached the bottom of its scrollbar track**. It's as if the scrollbar track thinks there's more scrollable overflow than there actually is.



Notes:
[i] As hinted at in the beginning of comment 2: in recent Nightlies, the extension icon may instead be a menu-entry in a "unified extensions" menu.
[ii] In older nightlies (until ~April 2022), the popup usually just stays blank for me the first time that I open it. But if I close & reopen it again, it populates as-expected.