sync: Specialize functions that fetch type root

sync/internal_api/public/read_node.h

 // 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.
 
 #ifndef SYNC_INTERNAL_API_PUBLIC_READ_NODE_H_
 #define SYNC_INTERNAL_API_PUBLIC_READ_NODE_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 19 matching lines @@
   // BaseNode implementation.
   virtual InitByLookupResult InitByIdLookup(int64 id) OVERRIDE;
   virtual InitByLookupResult InitByClientTagLookup(
       ModelType model_type,
       const std::string& tag) OVERRIDE;
 
   // There is always a root node, so this can't fail.  The root node is
   // never mutable, so root lookup is only possible on a ReadNode.
   void InitByRootLookup();
 
-  // Each server-created permanent node is tagged with a unique string.
-  // Look up the node with the particular tag.  If it does not exist,
-  // return false.
-  InitByLookupResult InitByTagLookup(const std::string& tag);
+  // Returns the type root node, if it exists.  This is usually created by the
+  // server during first sync.  Eventually, we plan to remove support for it
+  // from the protocol and have the client create the node instead.
+  InitByLookupResult InitTypeRoot(ModelType type);
+
+  // Returns a server-created and unique-server-tagged item.
+  //
+  // This functionality is only useful for bookmarks because only bookmarks
+  // have server-tagged items.  All other server-tagged items are type root
+  // nodes, which should be looked up with InitTypeRoot().
+  InitByLookupResult InitByTagLookupForBookmarks(const std::string& tag);
 
   // Implementation of BaseNode's abstract virtual accessors.
   virtual const syncable::Entry* GetEntry() const OVERRIDE;
   virtual const BaseTransaction* GetTransaction() const OVERRIDE;
 
  protected:
   ReadNode();
 
  private:
   void* operator new(size_t size);  // Node is meant for stack use only.
 
   // The underlying syncable object which this class wraps.
   syncable::Entry* entry_;
 
   // The sync API transaction that is the parent of this node.
   const BaseTransaction* transaction_;
 
   DISALLOW_COPY_AND_ASSIGN(ReadNode);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_READ_NODE_H_