Update {virtual,override,final} to follow C++11 style in ui.

ui/display/chromeos/x11/display_snapshot_x11.h

Index: ui/display/chromeos/x11/display_snapshot_x11.h
diff --git a/ui/display/chromeos/x11/display_snapshot_x11.h b/ui/display/chromeos/x11/display_snapshot_x11.h
index 35b5f68ea7efb3b84a5bb64075e817145c1ef3e6..95d75e85debf7e5d40f4a3edc2667226a023743f 100644
--- a/ui/display/chromeos/x11/display_snapshot_x11.h
+++ b/ui/display/chromeos/x11/display_snapshot_x11.h
@@ -30,14 +30,14 @@ class DISPLAY_EXPORT DisplaySnapshotX11 : public DisplaySnapshot {
                      RROutput output,
                      RRCrtc crtc,
                      int index);
-  virtual ~DisplaySnapshotX11();
+  ~DisplaySnapshotX11() override;
 
   RROutput output() const { return output_; }
   RRCrtc crtc() const { return crtc_; }
   int index() const { return index_; }
 
   // DisplaySnapshot overrides:
-  virtual std::string ToString() const override;
+  std::string ToString() const override;
 
  private:
   RROutput output_;