Affected versions
Nightly 79.0a1

Affected platforms
Devices with touchscreen(tested on Lenovo yoga)

Preconditions
apz.allow_zooming = true
apz.windows.use_direct_manipulation = true

Steps to reproduce
1. Navigate to a page which contains dropdown lists(e.g. https://twitter.com/i/flow/signup)
2. Tap to open a dropdown list(e.g. Month/Day)
3. Try to pinch zoom starting from the dropdown list

Expected result
APZ zooming is performed on the list

Actual Result
Reflow zooming is performed, zooming level is displayed in Address bar

Note
the actual behavior is the same when pinch gesture is initiated on Right-click context menu or on the opened Firefox hamburger menu

Not able to repro on macOS, it might be specific to Windows.

This is reproducible only with touchscreens.

Ah, I missed that in comment 0. Thanks for clarifying.

Tentatively marking this blocking nightly. Should be an easy-ish fix.

As far as I can tell this is not a regression specific to desktop zooming. It happens even with apz.allow_zooming=false and in a fresh install of Firefox 79.0. Something to fix, but maybe doesn't need to block desktop-zoom-release.