Affected versions

• 85.0a1(20201124092228)
• 84.0b4(20201122152513)

Affected platforms

• Windows 10x64
• Ubuntu 20x64
• macOS 10.14

Steps to reproduce

1. Launch FF.
2. Go to about:sessionrestore.
3. CTRL+P.
4. Uncheck the Print Backgrounds (if selected)

Expected result

• Only the Teddy sketch and the background color disappears.

Actual result

• Both the View Previous Tabs and Restore Session buttons disappear.

Suggested Severity

• I only managed to reproduce this issue in the specified about page. However , this issue may very well occur on other pages that use a similar implementation for buttons. I would suggest an S3

Regression range

• Will return with regression ASAP.

In a sense, the "Restore Session" button doesn't really disappear -- but it becomes invisible because its text color is white, and there's no longer a colored background on it.

As for the "View Previous Tabs" button, this seems to be triggered by the presence of background-image in its CSS; if I disable that rule, the text of the button remains visible in the print preview, but when background-image is enabled, the text is suppressed along with the background. That looks like a bug to me.

I've investigated this issue in order to find a regression range, but it seems that the bug also occurs on Nightly 81.0a1 (2020-07-27). Older builds than this version, don't have the new Print preview fully implemented. FWIW, this can be reproduced even with the old UI, on 60.0a1 (2018-02-02).