Affected versions

• 85.0a1 (2020-12-09);

Affected platforms

• macOS 10.15

Steps to reproduce

1. Launch Firefox, access https://www.youtube.com/
2. Click on the (youtubes) Settings or Youtube Apps button;
3. CTRL+P to trigger print preview;
4. Click to expand the More Settings section;
5. Click on the Scale section;
6. Change scale to 30%;

Expected result

• dropdown menus retain position even in preview;

Actual result

• dropdown menu is not displayed and at certain scale values the @mediaquerries from the site might take effect on the preview;

Regression range

• not a regression, as prior to this the menus were not displayed at all
• First bad: 2020-12-09 (today's build)
• Last good: 2020-12-09
• Pushlog: [URL] according to mozregression changeset b0cedadb2b2a46016e7ded90441448387416973c

Additional notes

• with 84.0 the menus are not displayed;
• S3/S4 as suggested severity since it's not such a common use-scenario;
• attached recording to illustrate the issue.