The problem seemed to come back in ver. 2.3.5. I was able to get it working by using the fix:

HtmlEditorConfig::get('cms')->setOption('content_css', 'cms/css/editor.css, mysite/css/editor.css');

Thanks, Banal (and Mohammed).

I was trying to get the editor.css file happening because, if I use "color: #FFFFFF" for the <p> tags in my typography.css, the white writing does not show up against the white background of TinyMCS. I am using 2.4.7.

I found that adding stuff to the editor.css file worked out of the box for Firefox but Chrome required your fix. Odd...