MD text buttons - implement focus ring.

ui/views/controls/button/md_text_button.h

Index: ui/views/controls/button/md_text_button.h
diff --git a/ui/views/controls/button/md_text_button.h b/ui/views/controls/button/md_text_button.h
index 605f93f229e4c204e63853c0c2ea8d58a19fb330..10a9e3a57ac90a1b4e785ac7b65c24f1d885f5fb 100644
--- a/ui/views/controls/button/md_text_button.h
+++ b/ui/views/controls/button/md_text_button.h
@@ -20,15 +20,26 @@ class VIEWS_EXPORT MdTextButton : public LabelButton {
                                            const base::string16& text);
 
   // LabelButton:
+  void Layout() override;
   SkColor GetInkDropBaseColor() const override;
   void SetText(const base::string16& text) override;
 
+ protected:
+  // LabelButton:
+  void OnFocus() override;
+  void OnBlur() override;
+
  private:
   MdTextButton(ButtonListener* listener);
   ~MdTextButton() override;
 
   ButtonInkDropDelegate ink_drop_delegate_;
 
+  // A child view to draw the focus ring. This is not done via a FocusPainter
+  // because it needs to paint to a layer so it can extend beyond the bounds of
+  // |this|.
+  views::View* focus_ring_;
+
   DISALLOW_COPY_AND_ASSIGN(MdTextButton);
 };