Standardize usage of virtual/override/final in extensions/

extensions/browser/guest_view/guest_view_base.cc

Index: extensions/browser/guest_view/guest_view_base.cc
diff --git a/extensions/browser/guest_view/guest_view_base.cc b/extensions/browser/guest_view/guest_view_base.cc
index 0dba70c50476ea42af872ef241d381d454f3691c..2fbbf603020c336a136e2271ac121090f84d6d1e 100644
--- a/extensions/browser/guest_view/guest_view_base.cc
+++ b/extensions/browser/guest_view/guest_view_base.cc
@@ -65,21 +65,21 @@ class GuestViewBase::EmbedderLifetimeObserver : public WebContentsObserver {
         destroyed_(false),
         guest_(guest) {}
 
-  virtual ~EmbedderLifetimeObserver() {}
+  ~EmbedderLifetimeObserver() override {}
 
   // WebContentsObserver implementation.
-  virtual void WebContentsDestroyed() override {
+  void WebContentsDestroyed() override {
     // If the embedder is destroyed then destroy the guest.
     Destroy();
   }
 
-  virtual void AboutToNavigateRenderView(
+  void AboutToNavigateRenderView(
       content::RenderViewHost* render_view_host) override {
     // If the embedder navigates then destroy the guest.
     Destroy();
   }
 
-  virtual void RenderProcessGone(base::TerminationStatus status) override {
+  void RenderProcessGone(base::TerminationStatus status) override {
     // If the embedder crashes, then destroy the guest.
     Destroy();
   }