EDK: Sprinkle some more |final| secret sauce.

mojo/edk/system/test/test_io_thread.h

 // 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.
 
 #ifndef MOJO_EDK_SYSTEM_TEST_TEST_IO_THREAD_H_
 #define MOJO_EDK_SYSTEM_TEST_TEST_IO_THREAD_H_
 
 #include "base/callback_forward.h"
 #include "base/threading/thread.h"
 #include "mojo/edk/embedder/platform_task_runner.h"
 #include "mojo/public/cpp/system/macros.h"
 
 namespace mojo {
 namespace system {
 namespace test {
 
 // Class to help create/run threads with I/O |MessageLoop|s in tests.
-class TestIOThread {
+class TestIOThread final {
  public:
   enum class StartMode { AUTO, MANUAL };
   explicit TestIOThread(StartMode start_mode);
   // Stops the I/O thread if necessary.
   ~TestIOThread();
 
   // |Start()|/|Stop()| should only be called from the main (creation) thread.
   // After |Stop()|, |Start()| may be called again to start a new I/O thread.
   // |Stop()| may be called even when the I/O thread is not started.
   void Start();
@@ skipping 19 matching lines @@
   bool io_thread_started_;
 
   MOJO_DISALLOW_COPY_AND_ASSIGN(TestIOThread);
 };
 
 }  // namespace test
 }  // namespace system
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_TEST_TEST_IO_THREAD_H_