[SyncFS] Migrate version management from MDDB to index classes

chrome/browser/sync_file_system/drive_backend/metadata_database.cc

 // Copyright 2013 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_file_system/drive_backend/metadata_database.h"
 
 #include <algorithm>
 #include <stack>
 
 #include "base/bind.h"
@@ skipping 266 matching lines @@
       return SYNC_DATABASE_ERROR_FAILED;
       // fall-through
     case 3:
       DCHECK_EQ(3, kCurrentDatabaseVersion);
       return SYNC_STATUS_OK;
     default:
       return SYNC_DATABASE_ERROR_FAILED;
   }
 }
 
-SyncStatusCode WriteVersionInfo(leveldb::DB* db) {
-  base::ThreadRestrictions::AssertIOAllowed();
-  DCHECK(db);
-  return LevelDBStatusToSyncStatusCode(
-      db->Put(leveldb::WriteOptions(),
-              kDatabaseVersionKey,
-              base::Int64ToString(kCurrentDatabaseVersion)));
-}
-
 bool HasInvalidTitle(const std::string& title) {
   return title.empty() ||
       title.find('/') != std::string::npos ||
       title.find('\\') != std::string::npos;
 }
 
 void MarkTrackerSetDirty(const TrackerIDSet& trackers,
                          MetadataDatabaseIndexInterface* index,
                          leveldb::WriteBatch* batch) {
   for (TrackerIDSet::const_iterator itr = trackers.begin();
@@ skipping 1166 matching lines @@
 
   SyncStatusCode status = SYNC_STATUS_UNKNOWN;
   bool created = false;
   // Open database unless |db_| is overridden for testing.
   if (!db_) {
     status = OpenDatabase(database_path_, env_override_, &db_, &created);
     if (status != SYNC_STATUS_OK)
       return status;
   }
 
-  if (created) {
-    status = WriteVersionInfo(db_.get());
-    if (status != SYNC_STATUS_OK)
-      return status;
-  } else {
+  if (!created) {
     status = MigrateDatabaseIfNeeded(db_.get());
     if (status != SYNC_STATUS_OK)
       return status;
   }
 
   leveldb::WriteBatch batch;
   index_ = MetadataDatabaseIndex::Create(db_.get(), &batch);
 
   status = LevelDBStatusToSyncStatusCode(
       db_->Write(leveldb::WriteOptions(), &batch));
@@ skipping 482 matching lines @@
   index_->StoreFileMetadata(app_root_metadata.Pass(), batch);
   index_->StoreFileTracker(app_root_tracker.Pass(), batch);
 }
 
 void MetadataDatabase::DetachFromSequence() {
   worker_sequence_checker_.DetachFromSequence();
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system