Eliminate Bookmarks dependence to bookmark_undo_utils.h.

chrome/browser/bookmarks/bookmark_model_observer.h

Index: chrome/browser/bookmarks/bookmark_model_observer.h
diff --git a/chrome/browser/bookmarks/bookmark_model_observer.h b/chrome/browser/bookmarks/bookmark_model_observer.h
index d9116e82ea5f3a8039611343353e30d2f0a0bdda..43c471912038254a9be70e6fb5182e26ca14bd2a 100644
--- a/chrome/browser/bookmarks/bookmark_model_observer.h
+++ b/chrome/browser/bookmarks/bookmark_model_observer.h
@@ -99,6 +99,14 @@ class BookmarkModelObserver {
   // Invoked when all non-permanent bookmark nodes have been removed.
   virtual void BookmarkAllNodesRemoved(BookmarkModel* model) = 0;
 
+  // Invoked before a set of model changes initiated by a single user action
+  // is about to begin.

[sky, 2014/02/06 17:48:27]

Give an example of what this entails, and one comment for the two should
suffice.

[Tom Cassiotis, 2014/02/21 17:51:45]

Done.

+  virtual void GroupedBookmarkChangesBeginning(BookmarkModel* model) {}
+
+  // Invoked after a set of model changes triggered by a single user action has
+  // ended.
+  virtual void GroupedBookmarkChangesEnded(BookmarkModel* model) {}
+
  protected:
   virtual ~BookmarkModelObserver() {}
 };