Add ability to underline links on hover in Views

ui/views/controls/link.h

Index: ui/views/controls/link.h
diff --git a/ui/views/controls/link.h b/ui/views/controls/link.h
index 5fcce6feada23132279a43f5955d438014966657..9e8631e76448bc4f1c9c1c1c78227c62d2b688cd 100644
--- a/ui/views/controls/link.h
+++ b/ui/views/controls/link.h
@@ -39,6 +39,9 @@ class VIEWS_EXPORT Link : public Label {
   virtual bool OnMouseDragged(const ui::MouseEvent& event) OVERRIDE;
   virtual void OnMouseReleased(const ui::MouseEvent& event) OVERRIDE;
   virtual void OnMouseCaptureLost() OVERRIDE;
+  virtual void OnMouseEntered(const ui::MouseEvent& event) OVERRIDE;
+  virtual void OnMouseExited(const ui::MouseEvent& event) OVERRIDE;
+
   virtual ui::EventResult OnGestureEvent(
       const ui::GestureEvent& event) OVERRIDE;
   virtual bool OnKeyPressed(const ui::KeyEvent& event) OVERRIDE;
@@ -51,6 +54,7 @@ class VIEWS_EXPORT Link : public Label {
 
   virtual void SetEnabledColor(SkColor color) OVERRIDE;
   void SetPressedColor(SkColor color);
+  void SetUnderlineOnHover(bool underline_on_hover);
 
   static const char kViewClassName[];
 
@@ -66,6 +70,12 @@ class VIEWS_EXPORT Link : public Label {
   // Whether the link is currently pressed.
   bool pressed_;
 
+  // Whether the link is underlined only on hover.
+  bool underline_on_hover_;
+
+  // Whether the mouse is hovering over the link.
+  bool mouse_inside_;
+
   // The color when the link is neither pressed nor disabled.
   SkColor requested_enabled_color_;