Affected versions

• Firefox 69.0a1 (20190702093917)

Affected platforms

• Windows 10 x64
• macOS 10.14

Preconditions

• Download and install https://archive.mozilla.org/pub/firefox/nightly/2019/07/2019-07-02-09-39-17-mozilla-central/ .
• Use NetLimiter to simulate a very poor connection (I set my limit to 5kb).
• Create a user.js with “user_pref("app.update.log", true);”.

Steps to reproduce

1. Launch Firefox and quickly go to Menu ->Help ->About Firefox.
2. Open Browser console and check for update progress.
3. Disable NeLimiter.

Expected result

• Same download progress is shown in UI and browser console.

Actual result

• If “Checking for updates” message is still present when About Firefox window is opened, it remains stuck in that place until closed and opened again.

Regression Range

• I cannot reproduce the issue on Firefox 69.0a1 (20190701095406). Generated a pushlog:

Last good revision: 0176f11e448f372c7d45dcff967d6773efda9ed5 (2019-07-01)
First bad revision: fd2778a2ce8ba1284cba867f4358f9fcaf795568 (2019-07-02)
Pushlog:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=0176f11e448f372c7d45dcff967d6773efda9ed5&tochange=fd2778a2ce8ba1284cba867f4358f9fcaf795568

Additional Notes

• I cannot reproduce the issue using the above steps on Firefox Developer Edition 69.0b1 (20190701201355).
• Note that the issue may be intermittent.
• The issue is reproducible using both nsIIncrementalDownload and BITS.
• Attached a screen recording with the issue.
• Attached a log from the browser console: link.

Thanks for filing this. I suspected there might be issues for this scenario but haven't had the time to check. Since this seldom if ever happens to users I'm marking this as fix-optional.

I have the same problem for Thunderbird Daily v100.0a1