Add virtual and OVERRIDE to base/ implementation files

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/file_path.h"
 #include "base/test/mock_devices_changed_observer.h"
 #include "base/system_monitor/system_monitor.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
 class PowerTest : public SystemMonitor::PowerObserver {
  public:
   PowerTest()
       : battery_(false),
         power_state_changes_(0),
         suspends_(0),
         resumes_(0) {
   }
 
   // PowerObserver callbacks.
-  void OnPowerStateChange(bool on_battery_power) {
+  virtual void OnPowerStateChange(bool on_battery_power) OVERRIDE {
     power_state_changes_++;
   }
 
-  void OnSuspend() {
+  virtual void OnSuspend() OVERRIDE {
     suspends_++;
   }
 
-  void OnResume() {
+  virtual void OnResume() OVERRIDE {
     resumes_++;
   }
 
   // Test status counts.
   bool battery() { return battery_; }
   int power_state_changes() { return power_state_changes_; }
   int suspends() { return suspends_; }
   int resumes() { return resumes_; }
 
  private:
@@ skipping 89 matching lines @@
   system_monitor.ProcessMediaDeviceAttached(
       1, "media device", FilePath(FILE_PATH_LITERAL("path")));
   loop.RunAllPending();
 
   system_monitor.ProcessMediaDeviceDetached(1);
   system_monitor.ProcessMediaDeviceDetached(2);
   loop.RunAllPending();
 }
 
 }  // namespace base