Fix the broken layout of CX source selector in Firefox

The input fields were aligned incorrectly. Fix it by wrapping them in
divs and apply grid properly

Change-Id: Ib5cf8661fd481af60eb6d0900d891e1dfd81de58
Remove the unused style for close icon in translation source selector

Close icon is not present in this dialog

Change-Id: I6138c0ba2a2832fa9a843142f179d56c67d2cb27
Merge "Fix the broken layout of CX source selector in Firefox"
Merge "Remove the unused style for close icon in translation source selector"