1202181 - Firefox application button in the task bar doesn't display tooltip with title after ~10 seconds Firefox was launched

Status: NEW

(Core :: Widget: Win32, defect)

Description

[arni2033]

STR:   (Win7_64, Nightly 43, 32bit, ID 20150901030226, new profile, safe mode)
1. Launch Firefox, make sure it has only 1 window.
2. Wait 10+ seconds (try to wait ~1 minute for sure)
3. Hover mouse over Firefox application button in the task bar

Result:       Windows' popup bubble with preview appeared, but tooltip with title isn't displayed
Expectations: Tooltip should appear

Actually, if I open new window, it always displays tooltip. But this is useless since 95% of sessions I store all my tabs in 1 window.

Comment 1

[arni2033]

If I manage to start Browser Toolbox before the title disappears (less than 10 seconds), open debugger and click "pause" button, then firefox window's title is displayed properly.
(Сlarification: Firefox window's title. Not browser toolbox's window title. The last one is always displayed properly. My report isn't about browser toolbox anyway. I hope that's clear)
When I click that button again, then firefox window's title disappears forever.

Note that this comment describes my research confirming that the bug exists.
The bug itself is described in comment 0.

Comment 2

[arni2033]

Wow, it's a regression between 2010-04-14 and 2010-04-15. Such a long-standing bug.
I tested it on profile with pre-defined pref   browser.taskbar.previews.enable -> false
Can't think of better suspect than bug 474060. Feel free to correct me.
> pushlog_url:   http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=fab327eb791b&tochange=d9d7de04f75d

Comment 3

[arni2033]

Improved STR:
1. Launch Firefox, make sure it has only 1 window.
2. Open the following "data:" url in a new tab:
>   data:text/html,<script>var S=''; for (i=0;i<999;i++) S+='t'; document.title=S;</script>
3. Wait 10+ seconds (try to wait ~1 minute for sure)
4. Hover mouse over Firefox application button in the task bar

AR: Windows' popup bubble with preview appeared, but tooltip with title isn't displayed
ER: Tooltip should appear

> screenshot:   https://dl.dropboxusercontent.com/s/l2iqpm7xmgeti2x/screenshot%201%20-%20Firefox%20application%20button%20doesn%27t%20display%20tooltip.png?dl=0