TinyMCE: add internal command and shortcut (Alt+Shift+X) for toggling <code>. Define a button that can be added to any toolbar as wp_code. See #6113

git-svn-id: https://develop.svn.wordpress.org/trunk@27545 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/css/editor.css

@@ -661,6 +661,10 @@ i.mce-i-wp_page:before {
 	content: '\f158';
 }
 
+.mce-i-wp_code:before {
+	content: "\e017";
+}
+
 /* Editors */
 .wp-editor-wrap {
 	position: relative;