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

chrome/browser/sync/glue/generic_change_processor.cc

 // 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.
 
 #include "chrome/browser/sync/glue/generic_change_processor.h"
 
 #include "base/location.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/sync/api/syncable_service.h"
 #include "chrome/browser/sync/api/sync_change.h"
@@ skipping 223 matching lines @@
   *has_nodes = false;
   sync_api::ReadTransaction trans(FROM_HERE, share_handle());
   sync_api::ReadNode type_root_node(&trans);
   if (!type_root_node.InitByTagLookup(syncable::ModelTypeToRootTag(type))) {
     LOG(ERROR) << err_str;
     return false;
   }
 
   // The sync model has user created nodes if the type's root node has any
   // children.
-  *has_nodes = sync_api::kInvalidId != type_root_node.GetFirstChildId();
+  *has_nodes = type_root_node.HasChildren();
   return true;
 }
 
 bool GenericChangeProcessor::CryptoReadyIfNecessary(syncable::ModelType type) {
   DCHECK(CalledOnValidThread());
   DCHECK_NE(type, syncable::UNSPECIFIED);
   // We only access the cryptographer while holding a transaction.
   sync_api::ReadTransaction trans(FROM_HERE, share_handle());
   const syncable::ModelTypeSet& encrypted_types =
       GetEncryptedTypes(&trans);
   return encrypted_types.count(type) == 0 ||
          trans.GetCryptographer()->is_ready();
 }
 
 void GenericChangeProcessor::StartImpl(Profile* profile) {
   DCHECK(CalledOnValidThread());
 }
 
 void GenericChangeProcessor::StopImpl() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 }
 
 sync_api::UserShare* GenericChangeProcessor::share_handle() const {
   DCHECK(CalledOnValidThread());
   return share_handle_;
 }
 
 }  // namespace browser_sync