Standardize usage of virtual/override/final in content/

content/plugin/plugin_thread.h

Index: content/plugin/plugin_thread.h
diff --git a/content/plugin/plugin_thread.h b/content/plugin/plugin_thread.h
index 1a9906a7bb7a533cb8f333a6b4476be48491634e..11acafc79c1b104da9dc79f4ed12e0e584301c2d 100644
--- a/content/plugin/plugin_thread.h
+++ b/content/plugin/plugin_thread.h
@@ -25,8 +25,8 @@ class BlinkPlatformImpl;
 class PluginThread : public ChildThread {
  public:
   PluginThread();
-  virtual ~PluginThread();
-  virtual void Shutdown() override;
+  ~PluginThread() override;
+  void Shutdown() override;
 
   // Returns the one plugin thread.
   static PluginThread* current();
@@ -36,7 +36,7 @@ class PluginThread : public ChildThread {
   void SetForcefullyTerminatePluginProcess();
 
  private:
-  virtual bool OnControlMessageReceived(const IPC::Message& msg) override;
+  bool OnControlMessageReceived(const IPC::Message& msg) override;
 
   // Callback for when a channel has been created.
   void OnCreateChannel(int renderer_id, bool incognito);