marijnh/CodeMirror — pull request #2564 by daveagp (2014-05-17 05:14:27+00:00)
Title: Have updateLineClasses keep existing classes, and add on new ones

In callbacks to "renderLine", the documentation suggests `The handler may mess with the style of the resulting (pre) element`. However, updateLineClasses is called afterwards, which completely replaces the class of that element with other stuff. This fix allows the classes assigned directly to that pre element to be retained.