Standardize usage of virtual/override/final specifiers in base/.

base/system_monitor/system_monitor_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/system_monitor/system_monitor.h"
 
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/test/mock_devices_changed_observer.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
 namespace {
 
 class SystemMonitorTest : public testing::Test {
  protected:
   SystemMonitorTest() {
     system_monitor_.reset(new SystemMonitor);
   }
-  virtual ~SystemMonitorTest() {}
 
   MessageLoop message_loop_;
   scoped_ptr<SystemMonitor> system_monitor_;
 
   DISALLOW_COPY_AND_ASSIGN(SystemMonitorTest);
 };
 
 TEST_F(SystemMonitorTest, DeviceChangeNotifications) {
   const int kObservers = 5;
 
@@ skipping 12 matching lines @@
   RunLoop().RunUntilIdle();
 
   system_monitor_->ProcessDevicesChanged(SystemMonitor::DEVTYPE_UNKNOWN);
   system_monitor_->ProcessDevicesChanged(SystemMonitor::DEVTYPE_UNKNOWN);
   RunLoop().RunUntilIdle();
 }
 
 }  // namespace
 
 }  // namespace base