1700888 - Autoscroll no longer works on about:* pages (except about:newtab)

Status: VERIFIED FIXED

(Core :: DOM: UI Events & Focus Handling, defect, P2)

Description

[Ciprian Muresan [:cmuresan], Ecosystem QA]

[Affected versions]:

• Firefox Nightly 89.0a1, Build ID 20210324160546

[Affected Platforms]:

• Windows 10
• macOS 10.15
• Ubuntu 20.04 (with general.autoScroll set to true)

[Prerequisites]:

• Have a new Firefox profile.

[Steps to reproduce]:

1. Open the browser with the profile from prerequisites.
2. Navigate to the about:support page.
3. Initiate an autoscroll event using the middle mouse button (scroll) and move the mouse down.
4. Observe the behavior.

[Expected results]:

• The page is scrolled downwards.

[Actual results]:

• Autoscroll is not triggered in the page.

[Regression Window]:
2:52.86 INFO: Last good revision: 630002d187a1f7c9a7c61dcf4b8fc110698b665b
2:52.86 INFO: First bad revision: 8fcec4a428e2b9b6595c69511aae4429881d0c52
2:52.86 INFO: Pushlog:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=630002d187a1f7c9a7c61dcf4b8fc110698b665b&tochange=8fcec4a428e2b9b6595c69511aae4429881d0c52

From the pushlog it looks like bug 1686662 has caused this.
@masayuki, could you please take a look at this?

[Notes]:

• The issue is also reproducible on the about:preferences, about:addons, about:telemetry pages.

Comment 1

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)(away 4/27 - 5/6)]

Sure.

Comment 2

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)(away 4/27 - 5/6)]

Attachment: Bug 1700888 - Make `AutoScrollParent` always consider starting autoscroll when it's requested in non-remote browser element r=Gijs!

When active tab loads about:* which is in the chrome process, focused element
is null. Therefore, the check whether the browser element of AutoScrollParent
is active tab or not does not work as expected. And the new check was added
for web apps which don't call preventDefault() properly after opening new
tab of a middle mouse button click. So, our chrome document must not require
this hack. So, we keep the old behavior when the browser is not a remote one.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/74a82f46f9ae
Make `AutoScrollParent` always consider starting autoscroll when it's requested in non-remote browser element r=Gijs

Comment 4

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/74a82f46f9ae

Comment 5

[Ciprian Muresan [:cmuresan], Ecosystem QA]

I have verified that the issue is no longer reproducible on as many about:* pages that had scrollbars (I used about:about) on the latest Nightly 89.0a1 (Build ID 20210331215444) using Windows 10, macOS 11.2.3, and Linux MX 4.19.