[Sync] Add HasChildren() function and use it instead of GetFirstChildId()

chrome/browser/sync/internal_api/base_node.h

 // Copyright (c) 2011 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 CHROME_BROWSER_SYNC_INTERNAL_API_BASE_NODE_H_
 #define CHROME_BROWSER_SYNC_INTERNAL_API_BASE_NODE_H_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 138 matching lines @@
 
   // Getter specific to the SESSIONS datatype.  Returns protobuf
   // data.  Can only be called if GetModelType() == SESSIONS.
   const sync_pb::SessionSpecifics& GetSessionSpecifics() const;
 
   const sync_pb::EntitySpecifics& GetEntitySpecifics() const;
 
   // Returns the local external ID associated with the node.
   int64 GetExternalId() const;
 
+  // Returns true iff this node has children.
+  bool HasChildren() const;
+
   // Return the ID of the node immediately before this in the sibling order.
   // For the first node in the ordering, return 0.
   int64 GetPredecessorId() const;
 
   // Return the ID of the node immediately after this in the sibling order.
   // For the last node in the ordering, return 0.
-  virtual int64 GetSuccessorId() const;
+  int64 GetSuccessorId() const;
 
   // Return the ID of the first child of this node.  If this node has no
   // children, return 0.
-  virtual int64 GetFirstChildId() const;
+  int64 GetFirstChildId() const;
 
   // These virtual accessors provide access to data members of derived classes.
   virtual const syncable::Entry* GetEntry() const = 0;
   virtual const BaseTransaction* GetTransaction() const = 0;
 
   // Dumps a summary of node info into a DictionaryValue and returns it.
   // Transfers ownership of the DictionaryValue to the caller.
   base::DictionaryValue* GetSummaryAsValue() const;
 
   // Dumps all node details into a DictionaryValue and returns it.
@@ skipping 35 matching lines @@
 
   friend class SyncApiTest;
   FRIEND_TEST_ALL_PREFIXES(SyncApiTest, GenerateSyncableHash);
 
   DISALLOW_COPY_AND_ASSIGN(BaseNode);
 };
 
 }  // namespace sync_api
 
 #endif  // CHROME_BROWSER_SYNC_INTERNAL_API_BASE_NODE_H_