file_manager: Migrate FILE thread to TaskScheduler

chrome/browser/chromeos/file_manager/file_watcher_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/chromeos/file_manager/file_watcher.h"
 
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
+#include "base/task_scheduler/task_scheduler.h"
 #include "content/public/test/test_browser_thread_bundle.h"
 #include "google_apis/drive/test_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace file_manager {
 namespace {
 
 using google_apis::test_util::CreateQuitCallback;
 using google_apis::test_util::CreateCopyResultCallback;
 
@@ skipping 101 matching lines @@
   // Start watching changes in the temporary directory.
   base::FilePath changed_path;
   bool watcher_created = false;
   bool on_change_error = false;
   base::RunLoop run_loop;
   file_watcher->WatchLocalFile(
       temp_dir.GetPath(),
       CreateQuitCallback(
           &run_loop, CreateCopyResultCallback(&changed_path, &on_change_error)),
       CreateCopyResultCallback(&watcher_created));
-  // Spin the message loop so the base::FilePathWatcher is created.
+  // Flush the task scheduler and spin the message loop and so the
+  // base::FilePathWatcher is created.
+  base::TaskScheduler::GetInstance()->FlushForTesting();
   base::RunLoop().RunUntilIdle();
   ASSERT_TRUE(watcher_created);
 
   // Create a temporary file in the temporary directory. The file watcher
   // should detect the change in the directory.
   base::FilePath temp_file_path;
   ASSERT_TRUE(
       base::CreateTemporaryFileInDir(temp_dir.GetPath(), &temp_file_path));
   // Wait until the directory change is notified.
   run_loop.Run();
   ASSERT_FALSE(on_change_error);
   ASSERT_EQ(temp_dir.GetPath().value(), changed_path.value());
 
   // This is ugly, but FileWatcher should be deleted explicitly here, and
-  // spin the message loop so the base::FilePathWatcher is deleted.
+  // flush the task scheduler, so the base::FilePathWatcher is deleted.
   // Otherwise, base::FilePathWatcher may detect a change when the temporary
   // directory is deleted, which may result in crash.
   file_watcher.reset();
-  base::RunLoop().RunUntilIdle();
+  base::TaskScheduler::GetInstance()->FlushForTesting();
 }
 
 }  // namespace
 }  // namespace file_manager.