Standardize usage of virtual/override/final specifiers.

ui/message_center/views/proportional_image_view.h

Index: ui/message_center/views/proportional_image_view.h
diff --git a/ui/message_center/views/proportional_image_view.h b/ui/message_center/views/proportional_image_view.h
index f92b4d889ee893288adbca9e001e2c3f55b8ea03..63e8e049b0e519dd300d3a6fe06eb07012ca19ed 100644
--- a/ui/message_center/views/proportional_image_view.h
+++ b/ui/message_center/views/proportional_image_view.h
@@ -14,12 +14,12 @@ namespace message_center {
 class ProportionalImageView : public views::View {
  public:
   ProportionalImageView(const gfx::ImageSkia& image, const gfx::Size& max_size);
-  virtual ~ProportionalImageView();
+  ~ProportionalImageView() override;
 
   // Overridden from views::View:
-  virtual gfx::Size GetPreferredSize() const override;
-  virtual int GetHeightForWidth(int width) const override;
-  virtual void OnPaint(gfx::Canvas* canvas) override;
+  gfx::Size GetPreferredSize() const override;
+  int GetHeightForWidth(int width) const override;
+  void OnPaint(gfx::Canvas* canvas) override;
 
  private:
   gfx::Size GetImageDrawingSize();