sync: Start moving away from PREV_ID and NEXT_ID

sync/engine/syncer_util.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 "sync/engine/syncer_util.h"
 
 #include <algorithm>
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 38 matching lines @@
 using syncable::IS_DIR;
 using syncable::IS_UNAPPLIED_UPDATE;
 using syncable::IS_UNSYNCED;
 using syncable::Id;
 using syncable::META_HANDLE;
 using syncable::MTIME;
 using syncable::MutableEntry;
 using syncable::NON_UNIQUE_NAME;
 using syncable::BASE_SERVER_SPECIFICS;
 using syncable::PARENT_ID;
-using syncable::PREV_ID;
 using syncable::SERVER_CTIME;
 using syncable::SERVER_IS_DEL;
 using syncable::SERVER_IS_DIR;
 using syncable::SERVER_MTIME;
 using syncable::SERVER_NON_UNIQUE_NAME;
 using syncable::SERVER_PARENT_ID;
 using syncable::SERVER_ORDINAL_IN_PARENT;
 using syncable::SERVER_SPECIFICS;
 using syncable::SERVER_VERSION;
 using syncable::UNIQUE_CLIENT_TAG;
@@ skipping 385 matching lines @@
     syncable::IndexedBitField inclusion_filter,
     syncable::MetahandleSet* inserted_items,
     std::vector<syncable::Id>* commit_ids) {
 
   if (!inserted_items->insert(item->Get(META_HANDLE)).second)
     return false;
   commit_ids->push_back(item->Get(ID));
   if (item->Get(IS_DEL))
     return true;  // Deleted items have no predecessors.
 
-  Id prev_id = item->Get(PREV_ID);
+  Id prev_id = item->GetPredecessorId();
   while (!prev_id.IsRoot()) {
     Entry prev(trans, GET_BY_ID, prev_id);
     CHECK(prev.good()) << "Bad id when walking predecessors.";
     if (!prev.Get(inclusion_filter))
       break;
     if (!inserted_items->insert(prev.Get(META_HANDLE)).second)
       break;
     commit_ids->push_back(prev_id);
-    prev_id = prev.Get(PREV_ID);
+    prev_id = prev.GetPredecessorId();
   }
   return true;
 }
 
 void AddPredecessorsThenItem(
     syncable::BaseTransaction* trans,
     syncable::Entry* item,
     syncable::IndexedBitField inclusion_filter,
     syncable::MetahandleSet* inserted_items,
     std::vector<syncable::Id>* commit_ids) {
@@ skipping 166 matching lines @@
   if (update.version() < target->Get(SERVER_VERSION)) {
     LOG(WARNING) << "Update older than current server version for "
                  << *target << " Update:"
                  << SyncerProtoUtil::SyncEntityDebugString(update);
     return VERIFY_SUCCESS;  // Expected in new sync protocol.
   }
   return VERIFY_UNDECIDED;
 }
 
 }  // namespace syncer