Affected versions

• 78.0esr (20200623021425)

Affected platforms

• Windows 10x64

Steps to reproduce

1. Open Firefox and a new tab.
2. Click on the search bar to open top sites.
3. Hold Shift key pressed and move the mouse to the right side and type @ string while almost to the end of the search bar.

Expected result

• Search engines are displayed as expected.

Actual result

• Topsites icons are overlapping search engine icons.

Regression range

• I will search for one ASAP but I think it may be difficult because the issue is intermittent.

Notes

• Attached a screen recording and a screenshot.

• The issue is intermittent and can be reproduced only with a new profile or after a restart.

• The icons are refreshed after moving the mouse over the search bar.

• Considering that it is a cosmetic issue and the functionality is not affected, I consider that it is an S4 issue.

it's likely we are not resetting something, moving the mouse freezes results and may confuse code

Hello! Attaching the regression range:
Last good revision: 17aa41e3cb7cdff3b94e26e351e29cc8b9bab18a (2020-04-22)
First bad revision: ff7eec7be698cd21d92755d709e08897100fa9c8 (2020-04-23)
Pushlog:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=17aa41e3cb7cdff3b94e26e351e29cc8b9bab18a&tochange=ff7eec7be698cd21d92755d709e08897100fa9c8
Possible regressor: bug 1628065.

Note that in this regression only twitter/Wikipedia icons where affected on the bad builds as seen in the screenshot.