[SyncFS] Remove usage of file task runner under drive_backend/

chrome/browser/sync_file_system/drive_backend/metadata_database_unittest.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 "base/bind.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 183 matching lines @@
     if (metadata_database_->FindTrackersByFileID(file_id, &trackers)) {
       EXPECT_FALSE(trackers.empty());
       return *trackers.begin();
     }
     return 0;
   }
 
   SyncStatusCode InitializeMetadataDatabase() {
     SyncStatusCode status = SYNC_STATUS_UNKNOWN;
     MetadataDatabase::Create(base::ThreadTaskRunnerHandle::Get(),
-                             base::ThreadTaskRunnerHandle::Get(),
                              database_dir_.path(),
                              in_memory_env_.get(),
                              CreateResultReceiver(&status,
                                                   &metadata_database_));
     message_loop_.RunUntilIdle();
     return status;
   }
 
   void DropDatabase() {
     metadata_database_.reset();
@@ skipping 946 matching lines @@
   EXPECT_TRUE(file->HasKey("details"));
 
   ASSERT_TRUE(files->GetDictionary(1, &file));
   EXPECT_TRUE(file->GetString("title", &str) && str == "file_0");
   EXPECT_TRUE(file->GetString("type", &str) && str == "file");
   EXPECT_TRUE(file->HasKey("details"));
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system