[Note]:

• On Ubuntu and Win 7 only works with Alt + Up/Down arrow keys but you can only scroll through the one click search engines it does not sets them as the default search engine.

[Affected versions]:

• Fx 67.0b3

[Affected platforms]:

• Windows 10
  mac 10.14
  Windows 7
  Ubuntu 18.04

Steps to reproduce:

1. Enable the search bar from about:preferences#search by clicking on "Add search bar in toolbar" option.
2. Write something in the search bar.
3. Try to scroll through the search engines using ctrl + up/down arrows.

Expected result:

• You can scroll through the search engines.

Actual result:

• You cant scroll through the search engines.

Regression range:

• https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=de93460e55c469f93834a87d5820d9d94c3d386e&tochange=63348118ef1d564a659f793c0ec9afe5d7f1cc8b

Additional notes:
*On Ubuntu and Win 7 only works with Alt + Up/Down arrow keys but you can only scroll through the one click search engines it does not sets them as the default search engine.