Documented that the new nodes at the root aren't meant to sync.

chrome/browser/sync/glue/bookmark_model_associator.cc

 // Copyright 2012 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/sync/glue/bookmark_model_associator.h"
 
 #include <stack>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 228 matching lines @@
     BookmarkNode::BOOKMARK_BAR,
     BookmarkNode::OTHER_NODE,
     BookmarkNode::MOBILE,
   };
   for (size_t i = 0; i < arraysize(bookmark_node_types); ++i) {
     int64 id = bookmark_model_->PermanentNode(bookmark_node_types[i])->id();
     bookmark_model_->SetPermanentNodeVisible(
       bookmark_node_types[i],
       id_map_.find(id) != id_map_.end());
   }
+
+  // Note: the root node may have additional extra nodes. Currently their
+  // visibility is not affected by sync.
 }
 
 syncer::SyncError BookmarkModelAssociator::DisassociateModels() {
   id_map_.clear();
   id_map_inverse_.clear();
   dirty_associations_sync_ids_.clear();
   return syncer::SyncError();
 }
 
 int64 BookmarkModelAssociator::GetSyncIdFromChromeId(const int64& node_id) {
@@ skipping 197 matching lines @@
 
   if (!AssociateTaggedPermanentNode(bookmark_model_->mobile_node(),
                                     kMobileBookmarksTag) &&
       expect_mobile_bookmarks_folder_) {
     return unrecoverable_error_handler_->CreateAndUploadError(
         FROM_HERE,
         "Mobile bookmarks node not found",
         model_type());
   }
 
+  // Note: the root node may have additional extra nodes. Currently none of
+  // them are meant to sync.
+
   int64 bookmark_bar_sync_id = GetSyncIdFromChromeId(
       bookmark_model_->bookmark_bar_node()->id());
   DCHECK_NE(bookmark_bar_sync_id, syncer::kInvalidId);
   int64 other_bookmarks_sync_id = GetSyncIdFromChromeId(
       bookmark_model_->other_node()->id());
   DCHECK_NE(other_bookmarks_sync_id, syncer::kInvalidId);
   int64 mobile_bookmarks_sync_id = GetSyncIdFromChromeId(
        bookmark_model_->mobile_node()->id());
   if (expect_mobile_bookmarks_folder_) {
     DCHECK_NE(syncer::kInvalidId, mobile_bookmarks_sync_id);
@@ skipping 132 matching lines @@
   if (bk_delete_journals.empty())
     return 0;
   size_t num_journals_unmatched = bk_delete_journals.size();
 
   // Check bookmark model from top to bottom.
   std::stack<const BookmarkNode*> dfs_stack;
   dfs_stack.push(bookmark_model_->bookmark_bar_node());
   dfs_stack.push(bookmark_model_->other_node());
   if (expect_mobile_bookmarks_folder_)
     dfs_stack.push(bookmark_model_->mobile_node());
+  // Note: the root node may have additional extra nodes. Currently none of
+  // them are meant to sync.
 
   // Remember folders that match delete journals in first pass but don't delete
   // them in case there are bookmarks left under them. After non-folder
   // bookmarks are removed in first pass, recheck the folders in reverse order
   // to remove empty ones.
   FolderInfoList folders_matched;
   while (!dfs_stack.empty()) {
     const BookmarkNode* parent = dfs_stack.top();
     dfs_stack.pop();
 
@@ skipping 147 matching lines @@
                                  syncer::SyncError::PERSISTENCE_ERROR,
                                  message,
                                  syncer::BOOKMARKS);
       }
     }
   }
   return syncer::SyncError();
 }
 
 }  // namespace browser_sync