Styles are hardcoded when text is moved (in Chrome)

I use CKEDITOR.config.contentsCss to apply a certain style to the contents of the editor.
All is working well, but when I select a heading and move it to another paragraph, styles are hardcoded all of a sudden.
After the move, a H1-tag looks something like this:
<h1 style="font-size: 25px; margin-bottom: 12px; margin-top: 10px;">.
Somehow the style from the stylesheet is hardcoded into the tags.

But it only happens in Chrome, in IE8 and FF tags are not changed!

Its easy to reconstruct it.
Download the zip-file from http://ckeditor.com/download
Edit the "ajax.html"-file
Add "CKEDITOR.config.contentsCss = 'XXXXXXXXXX.css';" after line 27
Test it in Chrome.

Any explanation?