Dropdown markers not grayed out when in readonly mode

[Marek Lewandowski]

Some part of our dropdown markers (an arrow) is not grayed out when readonly mode is set.

It would be good idea to keep behaviour consistent.

1. open CKEditor Read-Only sample (i.e. samples/readonly.html)
2. click "Make it read-only" button

Expected result:
Arrows in buttons for plugin like Text Color, Background Color, Set Language, SCAYT are not grayed out.

Current result:
Arrows should be grayed out the same way as icons are.

additional info:

1. Note that arrows for Styles/Format combo are grayed as expected.

[Jakub Ś]

Problem can be reproduced from CKEditor 4.0 (In beta it was the other way around).