Ticket #27416: 27416-01.patch

src/wp-includes/js/tinymce/plugins/wpview/plugin.js

@@ -140 +140 @@
         editor.on( 'SetContent', function( event ) {
                 var body, padNode;
 
-                wp.mce.views.render();
+                // don't (re-)render views if the format of the content is raw
+                // to avoid adding additional undo levels on undo/redo
+                if ( event.format !== 'raw' ) {
+                        wp.mce.views.render();
+                }
 
                 // Add padding <p> if the noneditable node is last
                 if ( event.load || ! event.set ) {