Experimental bookmark model based on tags.

chrome/browser/bookmarks/bookmark_tag_model.cc

+// Copyright (c) 2013 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.
+
+#include "chrome/browser/bookmarks/bookmark_tag_model.h"
+
+#include "base/json/json_string_value_serializer.h"
+#include "base/observer_list.h"
+#include "base/strings/string_util.h"
+#include "base/strings/utf_string_conversions.h"
+#include "chrome/browser/bookmarks/bookmark_model_factory.h"
+#include "chrome/browser/bookmarks/bookmark_tag_model_observer.h"
+#include "ui/base/models/tree_node_iterator.h"
+
+namespace {
+// The key used to store the tag list in the metainfo of a bookmark.
+const char* TAG_KEY = "TAG_KEY";
+
+// Predicates to sort bookmarks.
+bool CompareBookmarkTitles(const BookmarkNode* a, const BookmarkNode* b) {
+  return a->GetTitle() < b->GetTitle();
+}
+bool CompareBookmarkUrl(const BookmarkNode* a, const BookmarkNode* b) {
+  return a->url() < b->url();
+}
+bool CompareBookmarkCreation(const BookmarkNode* a, const BookmarkNode* b) {
+  return a->date_added() < b->date_added();
+}
+
+// Comparator to sort tags by usage.
+struct TagComparator {
+  TagComparator(std::map<BookmarkTag, unsigned int>& tags) : tags_(tags) {
+  }
+  ~TagComparator() {}
+
+  bool operator()(BookmarkTag a, BookmarkTag b) {
+    return (tags_[a] < tags_[b]);
+  }
+
+  std::map<BookmarkTag, unsigned int>& tags_;
+};
+}  // namespace
+
+BookmarkTagModel::BookmarkTagModel(BookmarkModel* bookmark_model)
+    : bookmark_model_(bookmark_model),
+      loaded_(false),
+      observers_(ObserverList<BookmarkTagModelObserver>::NOTIFY_EXISTING_ONLY),
+      inhibit_change_notifications_(false) {
+  bookmark_model_->AddObserver(this);
+  if (bookmark_model_->loaded())
+    Load();
+}
+
+BookmarkTagModel::~BookmarkTagModel() {
+  if (bookmark_model_)

[Yaron, 2013/10/11 10:50:41]

Can this ever fail? Seems like the c-tor guarantees you have one.

[noyau (Ping after 24h), 2013/10/11 12:09:21]

The bookmark model notifies its observer when it is going away, and I do clear
the bookmark_model_ instance variable then. See BookmarkModelBeingDeleted()
further down.

+    bookmark_model_->RemoveObserver(this);
+}
+
+#pragma mark BookmarkModel forwarding.
+
+void BookmarkTagModel::AddObserver(BookmarkTagModelObserver* observer) {
+  observers_.AddObserver(observer);
+}
+
+void BookmarkTagModel::RemoveObserver(BookmarkTagModelObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+void BookmarkTagModel::BeginExtensiveChanges() {
+  DCHECK(bookmark_model_);

[Yaron, 2013/10/11 10:50:41]

These DCHECKS all seem unnecessary for reasons above

[noyau (Ping after 24h), 2013/10/11 12:09:21]

These DCHECK are necessary for reasons above :)

+  bookmark_model_->BeginExtensiveChanges();
+}
+
+void BookmarkTagModel::EndExtensiveChanges() {
+  DCHECK(bookmark_model_);
+  bookmark_model_->EndExtensiveChanges();
+}
+
+bool BookmarkTagModel::IsDoingExtensiveChanges() const {
+  DCHECK(bookmark_model_);
+  return bookmark_model_->IsDoingExtensiveChanges();
+}
+
+void BookmarkTagModel::Remove(const BookmarkNode* bookmark) {
+  DCHECK(bookmark_model_);
+  DCHECK(loaded_);
+  const BookmarkNode *parent = bookmark->parent();
+  bookmark_model_->Remove(parent, parent->GetIndexOf(bookmark));
+}
+
+void BookmarkTagModel::RemoveAll() {
+  DCHECK(bookmark_model_);
+  DCHECK(loaded_);
+  bookmark_model_->RemoveAll();
+}
+
+const gfx::Image& BookmarkTagModel::GetFavicon(const BookmarkNode* bookmark) {
+  DCHECK(bookmark_model_);
+  DCHECK(loaded_);
+  return bookmark_model_->GetFavicon(bookmark);
+}
+
+void BookmarkTagModel::SetTitle(const BookmarkNode* bookmark,
+                                const string16& title) {
+  DCHECK(bookmark_model_);
+  DCHECK(loaded_);
+  bookmark_model_->SetTitle(bookmark, title);
+}
+
+void BookmarkTagModel::SetURL(const BookmarkNode* bookmark, const GURL& url) {
+  DCHECK(bookmark_model_);
+  DCHECK(loaded_);
+  bookmark_model_->SetURL(bookmark, url);
+}
+
+void BookmarkTagModel::SetDateAdded(const BookmarkNode* bookmark,
+                                    base::Time date_added) {
+  DCHECK(bookmark_model_);
+  DCHECK(loaded_);
+  bookmark_model_->SetDateAdded(bookmark, date_added);
+}
+
+const BookmarkNode*
+    BookmarkTagModel::GetMostRecentlyAddedBookmarkForURL(const GURL& url) {
+  DCHECK(bookmark_model_);
+  DCHECK(loaded_);
+  return bookmark_model_->GetMostRecentlyAddedNodeForURL(url);
+}
+
+#pragma mark Tags.
+
+const BookmarkNode* BookmarkTagModel::AddURL(
+    const string16& title,
+    const GURL& url,
+    const std::set<BookmarkTag>& tags) {
+  DCHECK(bookmark_model_);
+  DCHECK(loaded_);
+
+  inhibit_change_notifications_ = true;
+  const BookmarkNode* parent = bookmark_model_->GetParentForNewNodes();
+  const BookmarkNode* bookmark = bookmark_model_->AddURL(

[Yaron, 2013/10/11 10:50:41]

I'm pretty sure the underlying BookmarkModel will still fire notifications here.

[noyau (Ping after 24h), 2013/10/11 12:09:21]

Yes, it will, and should. This class relies on the notifications to update its
internal caches. This is just inhibiting the BookmarkTagModel notifications to
avoid sending two notifications, one that the node was created and second that
the tags where changed.

+      parent, 0, title, url);
+  AddTagsToBookmark(tags, bookmark);
+  inhibit_change_notifications_ = false;
+
+  FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                    BookmarkNodeAdded(this, bookmark));
+
+  return bookmark;
+}
+
+std::set<BookmarkTag>
+    BookmarkTagModel::AllTagsForBookmark(const BookmarkNode* bookmark) {
+  DCHECK(loaded_);
+  return bookmark_to_tags_[bookmark];
+}
+
+void BookmarkTagModel::AddTagsToBookmark(
+    const std::set<BookmarkTag>& tags, const BookmarkNode* bookmark) {
+  std::set<BookmarkTag> all_tags(AllTagsForBookmark(bookmark));
+  for (std::set<BookmarkTag>::iterator it = tags.begin();
+       it != tags.end(); ++it) {
+    BookmarkTag trimmed_tag = CollapseWhitespace(*it, true);
+    if (trimmed_tag.empty())
+      continue;
+    all_tags.insert(trimmed_tag);
+  }
+  ReplaceTagsOnBookmark(all_tags, bookmark);
+}
+
+void BookmarkTagModel::AddTagsToBookmarks(
+    const std::set<BookmarkTag>& tags,
+    const std::set<const BookmarkNode*>& bookmarks) {
+  for (std::set<const BookmarkNode*>::iterator it = bookmarks.begin();
+      it != bookmarks.end(); ++it) {
+    AddTagsToBookmark(tags, *it);
+  }
+}
+
+void BookmarkTagModel::RemoveTagsFromBookmark(
+    const std::set<BookmarkTag>& tags,
+    const BookmarkNode* bookmark) {
+  std::set<BookmarkTag> all_tags(AllTagsForBookmark(bookmark));
+  for (std::set<BookmarkTag>::iterator it = tags.begin();
+       it != tags.end(); ++it) {
+    all_tags.erase(*it);
+  }
+  ReplaceTagsOnBookmark(all_tags, bookmark);
+}
+
+void BookmarkTagModel::RemoveTagsFromBookmarks(
+    const std::set<BookmarkTag>& tags,
+    const std::set<const BookmarkNode*>& bookmarks){
+  for (std::set<const BookmarkNode*>::iterator it = bookmarks.begin();
+      it != bookmarks.end(); ++it) {
+    RemoveTagsFromBookmark(tags, *it);
+  }
+}
+
+std::vector<const BookmarkNode*> BookmarkTagModel::BookmarksForTags(
+    const std::set<BookmarkTag>& tags,
+    BookmarkTagModel::BookmarkOrdering ordering) {
+  DCHECK(loaded_);
+  std::set<const BookmarkNode*> bookmarks;
+  for (std::set<BookmarkTag>::iterator it = tags.begin();
+       it != tags.end(); ++it) {
+    const std::set<const BookmarkNode*> subset(tag_to_bookmarks_[*it]);
+    bookmarks.insert(subset.begin(), subset.end());

[noyau (Ping after 24h), 2013/10/11 12:09:21]

GCC on Android fail to compile this insert() with a very unclear error message.

+  }
+
+  std::vector<const BookmarkNode*> sorted_bookmarks(bookmarks.begin(),
+                                                    bookmarks.end());
+  switch (ordering) {
+    case UNSORTED_BOOKMARK_ORDERING:
+      break;
+    case TITLE_BOOKMARK_ORDERING:
+      std::sort(sorted_bookmarks.begin(), sorted_bookmarks.end(),
+                CompareBookmarkTitles);
+      break;
+    case URL_BOOKMARK_ORDERING:
+      std::sort(sorted_bookmarks.begin(), sorted_bookmarks.end(),
+                CompareBookmarkUrl);
+      break;
+    case CREATION_TIME_BOOKMARK_ORDERING:
+      std::sort(sorted_bookmarks.begin(), sorted_bookmarks.end(),
+                CompareBookmarkCreation);
+      break;
+    default:
+      NOTREACHED();
+  }
+  return sorted_bookmarks;
+}
+
+std::vector<const BookmarkNode*> BookmarkTagModel::BookmarksForTag(
+  const BookmarkTag& tag, BookmarkOrdering ordering) {
+  DCHECK(!tag.empty());
+  std::set<BookmarkTag> tagset;
+  tagset.insert(tag);
+  return BookmarksForTags(tagset, ordering);
+}
+
+std::vector<BookmarkTag> BookmarkTagModel::TagsRelatedToTag(
+    const BookmarkTag& tag, BookmarkTagModel::TagOrdering ordering) {
+  DCHECK(loaded_);
+  std::map<BookmarkTag, unsigned int> tags;
+
+  if (tag.empty()) {
+    // Returns all the tags.
+    for (std::map<const BookmarkTag, std::set<const BookmarkNode*> >::iterator
+        it = tag_to_bookmarks_.begin(); it != tag_to_bookmarks_.end(); ++it) {
+      tags[it->first] = it->second.size();
+    }
+  } else {
+    std::vector<const BookmarkNode*> bookmarks(
+        BookmarksForTag(tag, UNSORTED_BOOKMARK_ORDERING));
+
+    for (std::vector<const BookmarkNode*>::iterator it = bookmarks.begin();
+         it != bookmarks.end(); ++it) {
+      std::set<BookmarkTag> subset(bookmark_to_tags_[*it]);
+      for (std::set<BookmarkTag>::iterator tag_it = subset.begin();
+           tag_it != subset.end(); ++tag_it) {
+        tags[*tag_it] += 1;
+      }
+    }
+    tags.erase(tag);  // A tag is not related to itself.
+  }
+
+  // There is no keys() method on std::map. Nobody thought it might be useful?
+  std::vector<BookmarkTag> sorted_tags;
+  for (std::map<BookmarkTag, unsigned int>::iterator it = tags.begin();
+       it != tags.end(); ++it) {
+    sorted_tags.push_back(it->first);
+  }
+
+  switch (ordering) {
+    case UNSORTED_TAG_ORDERING:
+    case ALPHABETICAL_TAG_ORDERING:
+      break;  // std::map is already sorting its keys.
+    case MOST_USED_TAG_ORDERING:
+      std::sort(sorted_tags.begin(), sorted_tags.end(), TagComparator(tags));
+      break;
+    default:
+      NOTREACHED();
+  }
+  return sorted_tags;
+}
+
+#pragma mark Private methods.

[rlarocque, 2013/10/11 18:06:25]

What does this do?

[noyau (Ping after 24h), 2013/10/14 23:59:39]

Mac tools read those and use the text as a separator in the code outline. It's
just a hint to the IDE. But the windows compiler generate a warning on unknown
pragma, and the build treats warnings as errors, so I removed them all.

+
+std::set<BookmarkTag> BookmarkTagModel::ExtractTagsFromBookmark(
+    const BookmarkNode *bookmark) {
+  DCHECK(bookmark_model_);
+  // This is awful BTW. Metainfo is itself an encoded JSON, and here we decode
+  // another layer.
+
+  // Retrieve the encodedData from the bookmark. If there is no encoded data
+  // at all returns the name of all the ancestors as separate tags.
+  std::string encoded;
+  if (!bookmark->GetMetaInfo(TAG_KEY, &encoded)) {
+    std::set<BookmarkTag> tags;
+    const BookmarkNode* folder = bookmark->parent();
+    while (folder && folder->type() == BookmarkNode::FOLDER) {
+      BookmarkTag trimmed_tag = CollapseWhitespace(folder->GetTitle(), true);
+      if (!trimmed_tag.empty())
+        tags.insert(trimmed_tag);
+      folder = folder->parent();
+    }
+    return tags;
+  }
+
+  // Decode into a base::Value. If the data is not encoded properly as a list
+  // return an empty result.
+  JSONStringValueSerializer serializer(&encoded);
+  int error_code = 0;
+  std::string error_message;
+  base::Value* result = serializer.Deserialize(&error_code, &error_message);

[noyau (Ping after 24h), 2013/10/11 12:09:21]

Memory leak fixed (Thanks memory bot!)

+
+  if (error_code || !result->IsType(base::Value::TYPE_LIST))
+    return std::set<BookmarkTag>();
+
+  base::ListValue* list = NULL;
+  if (!result->GetAsList(&list) || list->empty())
+    return std::set<BookmarkTag>();
+
+  // Build the set.
+  std::set<BookmarkTag> return_value;
+
+  for (base::ListValue::iterator it = list->begin();
+       it != list->end(); ++it) {
+    base::Value* item = *it;
+    BookmarkTag tag;
+    if (!item->GetAsString(&tag))
+      continue;
+    return_value.insert(tag);
+  }
+  return return_value;
+}
+
+void BookmarkTagModel::ReplaceTagsOnBookmark(
+    const std::set<BookmarkTag>& tags, const BookmarkNode *bookmark) {
+  DCHECK(bookmark_model_);
+  DCHECK(loaded_);
+
+  // Build a ListValue.
+  std::vector<BookmarkTag> tag_vector(tags.begin(), tags.end());
+  base::ListValue list;
+  list.AppendStrings(tag_vector);
+
+  // Encodes it.
+  std::string encoded;
+  JSONStringValueSerializer serializer(&encoded);
+
+  // Pushes it in the bookmark's metainfo.
+  serializer.Serialize(list);
+  bookmark_model_->SetNodeMetaInfo(bookmark, TAG_KEY, encoded);
+}
+
+void BookmarkTagModel::Load() {
+  DCHECK(bookmark_model_);
+  DCHECK(!loaded_);
+  ui::TreeNodeIterator<const BookmarkNode> iterator(
+      bookmark_model_->root_node());
+  while (iterator.has_next())
+    LoadBookmark(iterator.Next());
+  loaded_ = true;
+  FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                    Loaded(this));
+}
+
+void BookmarkTagModel::LoadBookmark(const BookmarkNode* bookmark) {
+  DCHECK(bookmark_model_);
+  if (bookmark->is_url()) {
+    std::set<BookmarkTag> tags(ExtractTagsFromBookmark(bookmark));
+
+    bookmark_to_tags_[bookmark] = tags;
+    for (std::set<BookmarkTag>::iterator it = tags.begin();
+         it != tags.end(); ++it) {
+      tag_to_bookmarks_[*it].insert(bookmark);
+    }
+  }
+}
+
+void BookmarkTagModel::RemoveBookmark(const BookmarkNode* bookmark) {
+  DCHECK(bookmark_model_);
+  if (bookmark->is_url()) {
+    std::set<BookmarkTag> tags(bookmark_to_tags_[bookmark]);
+    bookmark_to_tags_.erase(bookmark);
+
+    for (std::set<BookmarkTag>::iterator it = tags.begin();
+         it != tags.end(); ++it) {
+      tag_to_bookmarks_[*it].erase(bookmark);
+      // Remove the tags no longer used.
+      if (!tag_to_bookmarks_[*it].size())
+        tag_to_bookmarks_.erase(*it);
+    }
+  }
+}
+
+#pragma mark BookmarkModelObserver.
+
+// Invoked when the model has finished loading.
+void BookmarkTagModel::Loaded(BookmarkModel* model, bool ids_reassigned) {
+  Load();
+};
+
+// Invoked from the destructor of the BookmarkModel.
+void BookmarkTagModel::BookmarkModelBeingDeleted(BookmarkModel* model) {
+  DCHECK(bookmark_model_);
+  FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                    BookmarkTagModelBeingDeleted(this));
+  bookmark_model_ = NULL;
+  observers_.Clear();
+}
+
+// Invoked when a node has moved.
+void BookmarkTagModel::BookmarkNodeMoved(BookmarkModel* model,
+                       const BookmarkNode* old_parent,
+                       int old_index,
+                       const BookmarkNode* new_parent,
+                       int new_index) {
+  DCHECK(loaded_);
+  const BookmarkNode* bookmark = new_parent->GetChild(new_index);
+  std::string encoded;
+  if (!bookmark->GetMetaInfo(TAG_KEY, &encoded)) {
+    // The bookmark moved and the system currently use its ancestors name as a
+    // poor approximation for tags.
+    FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                      OnWillChangeBookmarkTags(this, bookmark));
+    RemoveBookmark(bookmark);
+    LoadBookmark(bookmark);
+    FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                      BookmarkTagsChanged(this, bookmark));
+  }
+};
+
+// Invoked when a node has been added.
+void BookmarkTagModel::BookmarkNodeAdded(BookmarkModel* model,
+                       const BookmarkNode* parent,
+                       int index) {
+  DCHECK(loaded_);
+  const BookmarkNode* bookmark = parent->GetChild(index);
+  if (!bookmark->is_url())
+    return;
+  LoadBookmark(bookmark);
+
+  if (!inhibit_change_notifications_)
+    FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                      BookmarkNodeAdded(this, bookmark));
+}
+
+// Invoked before a node is removed.
+// |parent| the parent of the node that will be removed.
+// |old_index| the index of the node about to be removed in |parent|.
+// |node| is the node to be removed.
+void BookmarkTagModel::OnWillRemoveBookmarks(BookmarkModel* model,
+                                             const BookmarkNode* parent,
+                                             int old_index,
+                                             const BookmarkNode* node) {
+  DCHECK(loaded_);
+  RemoveBookmark(node);
+  FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                    OnWillRemoveBookmarks(this, node));
+}
+
+// Invoked when a node has been removed, the item may still be starred though.
+// |parent| the parent of the node that was removed.
+// |old_index| the index of the removed node in |parent| before it was
+// removed.
+// |node| is the node that was removed.
+void BookmarkTagModel::BookmarkNodeRemoved(BookmarkModel* model,
+                         const BookmarkNode* parent,
+                         int old_index,
+                         const BookmarkNode* node) {
+  DCHECK(loaded_);
+  FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                    BookmarkNodeRemoved(this, node));
+}
+
+// Invoked before the title or url of a node is changed.
+void BookmarkTagModel::OnWillChangeBookmarkNode(BookmarkModel* model,
+                              const BookmarkNode* node) {
+  DCHECK(loaded_);
+  if (!inhibit_change_notifications_)
+    FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                      OnWillChangeBookmarkNode(this, node));
+}
+
+// Invoked when the title or url of a node changes.
+void BookmarkTagModel::BookmarkNodeChanged(BookmarkModel* model,
+                                           const BookmarkNode* node) {
+  DCHECK(loaded_);
+  if (!inhibit_change_notifications_)
+    FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                      BookmarkNodeChanged(this, node));
+}
+
+// Invoked before the metainfo of a node is changed.
+void BookmarkTagModel::OnWillChangeBookmarkMetaInfo(BookmarkModel* model,
+                                                    const BookmarkNode* node) {
+  DCHECK(loaded_);
+  if (!inhibit_change_notifications_)
+    FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                      OnWillChangeBookmarkTags(this, node));
+}
+
+// Invoked when the metainfo on a node changes.
+void BookmarkTagModel::BookmarkMetaInfoChanged(BookmarkModel* model,
+                                     const BookmarkNode* node) {
+  DCHECK(loaded_);
+  RemoveBookmark(node);
+  LoadBookmark(node);
+  if (!inhibit_change_notifications_)
+    FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                      BookmarkTagsChanged(this, node));
+}
+
+// Invoked when a favicon has been loaded or changed.
+void BookmarkTagModel::BookmarkNodeFaviconChanged(BookmarkModel* model,
+                                const BookmarkNode* node) {
+  DCHECK(loaded_);
+  FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                    BookmarkNodeFaviconChanged(this, node));
+}
+
+// Invoked before the direct children of |node| have been reordered in some
+// way, such as sorted.
+void BookmarkTagModel::OnWillReorderBookmarkNode(BookmarkModel* model,
+                               const BookmarkNode* node) {
+  // This model doesn't care.
+}
+
+// Invoked when the children (just direct children, not descendants) of
+// |node| have been reordered in some way, such as sorted.
+void BookmarkTagModel::BookmarkNodeChildrenReordered(BookmarkModel* model,
+                                   const BookmarkNode* node) {
+  // This model doesn't care.
+}
+
+// Invoked before an extensive set of model changes is about to begin.
+// This tells UI intensive observers to wait until the updates finish to
+// update themselves.
+// These methods should only be used for imports and sync.
+// Observers should still respond to BookmarkNodeRemoved immediately,
+// to avoid holding onto stale node pointers.
+void BookmarkTagModel::ExtensiveBookmarkChangesBeginning(BookmarkModel* model) {
+  DCHECK(loaded_);
+  FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                    ExtensiveBookmarkChangesBeginning(this));
+}
+
+// Invoked after an extensive set of model changes has ended.
+// This tells observers to update themselves if they were waiting for the
+// update to finish.
+void BookmarkTagModel::ExtensiveBookmarkChangesEnded(BookmarkModel* model) {
+  DCHECK(loaded_);
+  FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                    ExtensiveBookmarkChangesEnded(this));
+}
+
+// Invoked before all non-permanent bookmark nodes are removed.
+void BookmarkTagModel::OnWillRemoveAllBookmarks(BookmarkModel* model) {
+  DCHECK(loaded_);
+  FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                    OnWillRemoveAllBookmarks(this));
+}
+
+// Invoked when all non-permanent bookmark nodes have been removed.
+void BookmarkTagModel::BookmarkAllNodesRemoved(BookmarkModel* model){
+  DCHECK(loaded_);
+  tag_to_bookmarks_.clear();
+  bookmark_to_tags_.clear();
+  FOR_EACH_OBSERVER(BookmarkTagModelObserver, observers_,
+                    BookmarkAllNodesRemoved(this));
+}