Currently, only the location of template files is cached by the override cache, so no checking for where the files are is needed on each request.

For CSS / JavaScript / images, each time a page is requested, the file need to be searched for in all design directories (including those in extensions). See eZTemplateDesignResource::fileMatch().

For example, in the admin interface, with approximately 19 design extensions, for the setup/info view, , there are about 24 file_exists calls for ezjsselection.js.

We should cache the final location of CSS / JavaScript files as well. Especially on slower file systems this will give a noticeable performance boost.