Improve loading of editor css

[azaozz]

Each TinyMCE plugin can add a stylesheet to the editor. We've been using this method for the extra css needed by our custom plugins. However we also have a customized theme that includes a stylesheet.

Instead of loading several (small) stylesheets we can combine all styles needed by our plugins into the theme's stylesheet. This will optimize the editor loading a little: few less requests.

In [19990]:

TinyMCE: move the WordPress plugins styles to the theme's stylesheet, fixes #20118

Did ed.dom.loadCSS(url + '/css/content.css'); only apply to our plugins, or would it apply to a custom/external plugin?

Replying to nacin:

It's a function in the MCE API, any plugin (including the default plugins) can use it to load another stylesheet in the editor. For our custom plugins it doesn't make sense to use it as we also have a custom theme for the editor and can add all needed css there.