Dropdown list selection remains if moving mouse away from list and trying to type in for another option

[cfogelSV]

Affected versions

• 81.0a1 (2020-08-16)

Affected platforms

• Windows 10, macOS 11.0

Steps to reproduce
pdfjs.renderInteractiveForms - enabled

1. Launch Firefox;
2. Access a PDF form with dropdown menus;
3. Click on the Country menu;
4. Type anything so any country is selected;
5. Move the mouse cursor away from the menu;
6. Reopen the dropdown menu and Type anything again (ex. Italy);
7. Type in any other country;

Expected result

• selection is made for the new country, since nothing from the menu is hovered over;

Actual result

• list item remains selected until moving mouse;

Additional notes:

• S3 as suggested severity;
  attached gif with the issue;