Standardize usage of virtual/override/final in net/

net/base/network_config_watcher_mac.cc

Index: net/base/network_config_watcher_mac.cc
diff --git a/net/base/network_config_watcher_mac.cc b/net/base/network_config_watcher_mac.cc
index 7d2377cc3fe3f0ce46348081bc2cd2ea6a857cb4..bdf75c39ad2a8ac677386bfa760a133446eb18e2 100644
--- a/net/base/network_config_watcher_mac.cc
+++ b/net/base/network_config_watcher_mac.cc
@@ -31,12 +31,12 @@ void DynamicStoreCallback(SCDynamicStoreRef /* store */,
 class NetworkConfigWatcherMacThread : public base::Thread {
  public:
   NetworkConfigWatcherMacThread(NetworkConfigWatcherMac::Delegate* delegate);
-  virtual ~NetworkConfigWatcherMacThread();
+  ~NetworkConfigWatcherMacThread() override;
 
  protected:
   // base::Thread
-  virtual void Init() override;
-  virtual void CleanUp() override;
+  void Init() override;
+  void CleanUp() override;
 
  private:
   // The SystemConfiguration calls in this function can lead to contention early