[MD Bookmarks] Fix singleton tab behavior.

components/bookmarks/browser/bookmark_model.cc

Index: components/bookmarks/browser/bookmark_model.cc
diff --git a/components/bookmarks/browser/bookmark_model.cc b/components/bookmarks/browser/bookmark_model.cc
index f9d58ceeafbcdef3d4b63d51ae60b472722c2180..29a68ae25f6d5c327e90531d8e5b675003803f19 100644
--- a/components/bookmarks/browser/bookmark_model.cc
+++ b/components/bookmarks/browser/bookmark_model.cc
@@ -110,6 +110,10 @@ class EmptyUndoDelegate : public BookmarkUndoDelegate {
 
 // BookmarkModel --------------------------------------------------------------
 
+const int64_t BookmarkModel::BOOKMARKS_BAR_NODE_ID = 1;

[sky, 2017/05/25 18:07:05]

Rather than exposing these, how about using bookmark_bar_node()->id()?

[calamity, 2017/05/26 03:33:34]

Done.

+const int64_t BookmarkModel::OTHER_BOOKMARKS_NODE_ID = 2;
+const int64_t BookmarkModel::MOBILE_BOOKMARKS_NODE_ID = 3;
+
 BookmarkModel::BookmarkModel(std::unique_ptr<BookmarkClient> client)
     : client_(std::move(client)),
       loaded_(false),
@@ -1023,12 +1027,15 @@ BookmarkPermanentNode* BookmarkModel::CreatePermanentNode(
   int title_id;
   switch (type) {
     case BookmarkNode::BOOKMARK_BAR:
+      DCHECK_EQ(BOOKMARKS_BAR_NODE_ID, node->id());
       title_id = IDS_BOOKMARK_BAR_FOLDER_NAME;
       break;
     case BookmarkNode::OTHER_NODE:
+      DCHECK_EQ(OTHER_BOOKMARKS_NODE_ID, node->id());
       title_id = IDS_BOOKMARK_BAR_OTHER_FOLDER_NAME;
       break;
     case BookmarkNode::MOBILE:
+      DCHECK_EQ(MOBILE_BOOKMARKS_NODE_ID, node->id());
       title_id = IDS_BOOKMARK_BAR_MOBILE_FOLDER_NAME;
       break;
     default: