Support undoing offline page deletion

components/bookmarks/browser/bookmark_model_observer.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_BOOKMARKS_BROWSER_BOOKMARK_MODEL_OBSERVER_H_
 #define COMPONENTS_BOOKMARKS_BROWSER_BOOKMARK_MODEL_OBSERVER_H_
 
 #include <set>
 
+#include "base/basictypes.h"
+
 class GURL;
 
 namespace bookmarks {
 
 class BookmarkModel;
 class BookmarkNode;
 
 // Observer for the BookmarkModel.
 class BookmarkModelObserver {
  public:
@@ skipping 107 matching lines @@
 
   // Invoked before a set of model changes that is initiated by a single user
   // action. For example, this is called a single time when pasting from the
   // clipboard before each pasted bookmark is added to the bookmark model.
   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) {}
 
+  // Invoked when a bookmark id has been renumbered when an undo operation
+  // occurs.
+  virtual void BookmarkNodeRenumbered(
+      BookmarkModel* model, int64 old_id, int64 new_id) {}

[sky, 2015/09/25 15:54:44]

int64_t on these. And this description is a bit confusing. You need to clarify
it.
Can you outline how you are using this function? This function is confusing
because it assumes you're keeping track of ids as they are changed. Why do you
need that?

[jianli, 2015/09/25 20:29:24]

Changed to use int64_t and updated the comment.

This is needed to support undoing deleting a bookmark with offline page saved.
For a bookmark with offline page, the offline metadata is persisted in a
different data store that is keyed by bookmark_id. When the undo occurs, the new
bookmark (with new ID) is cloned from the deleted one. To support restoring the
offline data, we need to do the following 2 things:
1) Postpone deleting the offline metadata (and hence offline file) by marking
the offline metadata for deletion.
2) When the new bookmark corresponding to the restored old one is created, we
need to update the bookmark id used in the offline metadata. Thus we need to
know about the renumber event.

[sky, 2015/09/25 20:38:57]

I think bookmark undo should be changed such that it adds back the old item.
This way you don't need to do anything here. This change should be done
separately.

+
  protected:
   virtual ~BookmarkModelObserver() {}
 };
 
 }  // namespace bookmarks
 
 #endif  // COMPONENTS_BOOKMARKS_BROWSER_BOOKMARK_MODEL_OBSERVER_H_