Repro (on desktop):

1. With Site Isolation enabled, open DevTools and enable device emulation.
2. Navigate to jsfiddle.net, paste the following HTML:
<select><option>option 1</option> </select>
3. Run the page.
4. Click the select element.

Notice the menu is quite far off from where it is supposed to be.

You can repro on a Chromebook without device emulation.

This doesn't repro on Mac or Android, presumably because they have different systems for displaying page popup widgets.

It seems that page scale factor isn't correctly being accounted for in where the menu is displayed. Context menu positions all seem to be correct even though their positioning mostly works in the same way.