leveldb: Add DBTracker for exposing databases to Chrome's memory-infra.

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 <utility>
 
@@ skipping 206 matching lines @@
 
   leveldb::Options options;
   options.max_open_files = 0;  // Use minimum.
   options.create_if_missing = true;
   options.paranoid_checks = true;
   options.reuse_logs = leveldb_env::kDefaultLogReuseOptionValue;
   if (env_override)
     options.env = env_override;
   leveldb::DB* db = nullptr;
   leveldb::Status db_status =
-      leveldb::DB::Open(options, path.AsUTF8Unsafe(), &db);
+      leveldb_env::DBRegistry::Open(options, path.AsUTF8Unsafe(), &db);
   UMA_HISTOGRAM_ENUMERATION("SyncFileSystem.Database.Open",
                             leveldb_env::GetLevelDBStatusUMAValue(db_status),
                             leveldb_env::LEVELDB_STATUS_MAX);
   SyncStatusCode status = LevelDBStatusToSyncStatusCode(db_status);
   if (status != SYNC_STATUS_OK) {
     delete db;
     return status;
   }
 
   db_out->reset(new LevelDBWrapper(base::WrapUnique(db)));
@@ skipping 1567 matching lines @@
       return false;
 
   if (!parents.empty())
     return false;
 
   return true;
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system