Index: CKEditor/trunk/_source/plugins/undo/plugin.js
===================================================================
--- CKEditor/trunk/_source/plugins/undo/plugin.js	(revision 6348)
+++ CKEditor/trunk/_source/plugins/undo/plugin.js	(revision 6461)
@@ -149,4 +149,7 @@
 	{
 		this.editor = editor;
+
+		editor.fire( 'beforeUndoImage' );
+
 		var contents = editor.getSnapshot(),
 			selection	= contents && editor.getSelection();
@@ -157,4 +160,6 @@
 		this.contents	= contents;
 		this.bookmarks	= selection && selection.createBookmarks2( true );
+
+		editor.fire( 'afterUndoImage' );
 	};
 
@@ -553,2 +558,22 @@
  * @event
  */
+
+/**
+ * Fired before an undo image is to be taken. An undo image represents the
+ * editor state at some point. It's saved into an undo store, so the editor is
+ * able to recover the editor state on undo and redo operations.
+ * @name CKEDITOR.editor#beforeUndoImage
+ * @since 3.5.3
+ * @see CKEDITOR.editor#afterUndoImage
+ * @event
+ */
+
+/**
+ * Fired after an undo image is taken. An undo image represents the
+ * editor state at some point. It's saved into an undo store, so the editor is
+ * able to recover the editor state on undo and redo operations.
+ * @name CKEDITOR.editor#afterUndoImage
+ * @since 3.5.3
+ * @see CKEDITOR.editor#beforeUndoImage
+ * @event
+ */