Standardize usage of virtual/override/final in ui/

ui/compositor/test/test_compositor_host_mac.mm

Index: ui/compositor/test/test_compositor_host_mac.mm
diff --git a/ui/compositor/test/test_compositor_host_mac.mm b/ui/compositor/test/test_compositor_host_mac.mm
index da3a8c24ccf2830fd9a9ac0860bc4ff487a6dea8..b262a21a85c03ebc838bc3ac9c123bb446cb9b5b 100644
--- a/ui/compositor/test/test_compositor_host_mac.mm
+++ b/ui/compositor/test/test_compositor_host_mac.mm
@@ -71,8 +71,7 @@ class AppKitHost : public FoundationHost {
   AppKitHost() {
     [NSApplication sharedApplication];
   }
-  virtual ~AppKitHost() {
-  }
+  ~AppKitHost() override {}
  private:
   DISALLOW_COPY_AND_ASSIGN(AppKitHost);
 };
@@ -84,12 +83,12 @@ class TestCompositorHostMac : public TestCompositorHost,
  public:
   TestCompositorHostMac(const gfx::Rect& bounds,
                         ui::ContextFactory* context_factory);
-  virtual ~TestCompositorHostMac();
+  ~TestCompositorHostMac() override;
 
  private:
   // TestCompositorHost:
-  virtual void Show() override;
-  virtual ui::Compositor* GetCompositor() override;
+  void Show() override;
+  ui::Compositor* GetCompositor() override;
 
   gfx::Rect bounds_;