[Components] Firefox: Some icons on components shown in a wrong smaller size

[wwwysocki]

Prepare:

1. Edit a component's XML file.
2. Remove the pal:icon attribute to use the default ("lightning") icon, OR
   set the the pal:icon attribute to "next", "parameter", image-right", or "image-left".
3. Save the changes

Repro:

1. Use Firefox
2. Insert > Component
3. Check for the component you've prepared.

Expected: The icon is of a large size.
Actual: The icon is of a small size.

Note: Compare to the same icons in other browsers, for example, Chrome.

Firefox (small icons):

Chrome (regular icons):

[wwwysocki]

Verified on 20170130.4