views::LabelButton should not call virtual methods from its constructor

ui/views/controls/button/blue_button.h

Index: ui/views/controls/button/blue_button.h
diff --git a/ui/views/controls/button/blue_button.h b/ui/views/controls/button/blue_button.h
index 6335f0ac426e25d140cbed07beb786ac1a03110c..adec3aeafd44bbcc141ba3034b3c8d3ceb403854 100644
--- a/ui/views/controls/button/blue_button.h
+++ b/ui/views/controls/button/blue_button.h
@@ -10,12 +10,15 @@
 
 namespace views {
 
-// A class representing a blue button.
-class VIEWS_EXPORT BlueButton : public LabelButton {
+// A class representing a blue button. Declared final because the constructor
+// calls virtual methods.
+class VIEWS_EXPORT BlueButton final : public LabelButton {
  public:
   static const char kViewClassName[];
 
+  // Constructs a BlueButton and initializes with LabelButton::InitAsButton().
   BlueButton(ButtonListener* listener, const base::string16& text);
+
   ~BlueButton() override;
 
  private: