Rewrite base::Bind into base::BindOnce on trivial cases in base

base/files/file_path_watcher_unittest.cc

 // Copyright (c) 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 "base/files/file_path_watcher.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #include <aclapi.h>
 #elif defined(OS_POSIX)
@@ skipping 38 matching lines @@
 // Aggregates notifications from the test delegates and breaks the message loop
 // the test thread is waiting on once they all came in.
 class NotificationCollector
     : public base::RefCountedThreadSafe<NotificationCollector> {
  public:
   NotificationCollector() : task_runner_(base::ThreadTaskRunnerHandle::Get()) {}
 
   // Called from the file thread by the delegates.
   void OnChange(TestDelegate* delegate) {
     task_runner_->PostTask(
-        FROM_HERE, base::Bind(&NotificationCollector::RecordChange, this,
-                              base::Unretained(delegate)));
+        FROM_HERE, base::BindOnce(&NotificationCollector::RecordChange, this,
+                                  base::Unretained(delegate)));
   }
 
   void Register(TestDelegate* delegate) {
     delegates_.insert(delegate);
   }
 
   void Reset() {
     signaled_.clear();
   }
 
@@ skipping 792 matching lines @@
   // longer access the file
   ASSERT_TRUE(ChangeFilePermissions(test_dir1, Execute, false));
   ASSERT_TRUE(WaitForEvents());
   ASSERT_TRUE(ChangeFilePermissions(test_dir1, Execute, true));
 }
 
 #endif  // OS_MACOSX
 }  // namespace
 
 }  // namespace base