Only include extra TinyMCE stylesheets once. props SergeyBiryukov. Fixes #18456

git-svn-id: http://svn.automattic.com/wordpress/trunk@18571 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-editor.php

@@ -294,6 +294,7 @@ class WP_Editor {
 				// load editor_style.css if the current theme supports it
 				if ( ! empty( $editor_styles ) && is_array( $editor_styles ) ) {
 					$mce_css = array();
+					$editor_styles = array_unique($editor_styles);
 					$style_uri = get_stylesheet_directory_uri();
 					if ( ! is_child_theme() ) {
 						foreach ( $editor_styles as $file )