Standardize usage of virtual/override/final in content/renderer/

content/renderer/idle_user_detector.h

Index: content/renderer/idle_user_detector.h
diff --git a/content/renderer/idle_user_detector.h b/content/renderer/idle_user_detector.h
index 516706b5f52d9546960bd5199e3ef418c08273d4..86a7eac6f355f630481acf83e7314d0b5f8e6c09 100644
--- a/content/renderer/idle_user_detector.h
+++ b/content/renderer/idle_user_detector.h
@@ -23,11 +23,11 @@ namespace content {
 class IdleUserDetector : public RenderViewObserver {
  public:
   IdleUserDetector(RenderView* render_view);
-  virtual ~IdleUserDetector();
+  ~IdleUserDetector() override;
 
  private:
   // RenderViewObserver implementation:
-  virtual bool OnMessageReceived(const IPC::Message& message) override;
+  bool OnMessageReceived(const IPC::Message& message) override;
 
   void OnHandleInputEvent(const blink::WebInputEvent* event,
                           const ui::LatencyInfo& latency_info,