Retrieve pinned flag directly from Notification class

ui/message_center/views/message_view.h

Index: ui/message_center/views/message_view.h
diff --git a/ui/message_center/views/message_view.h b/ui/message_center/views/message_view.h
index 147e99414561d4a78f28d029fa7d2ed214e33533..ed30d69412aa7a121bbba898fa3c41e6dcd6e6b7 100644
--- a/ui/message_center/views/message_view.h
+++ b/ui/message_center/views/message_view.h
@@ -52,7 +52,6 @@ class MESSAGE_CENTER_EXPORT MessageView : public views::SlideOutView {
 
   virtual bool IsCloseButtonFocused() const = 0;
   virtual void RequestFocusOnCloseButton() = 0;
-  virtual bool IsPinned() const = 0;
   virtual void UpdateControlButtonsVisibility() = 0;
 
   void OnCloseButtonPressed();
@@ -74,6 +73,7 @@ class MESSAGE_CENTER_EXPORT MessageView : public views::SlideOutView {
   std::string notification_id() { return notification_id_; }
   NotifierId notifier_id() { return notifier_id_; }
   const base::string16& display_source() const { return display_source_; }
+  bool pinned() const { return pinned_; }
 
   void set_controller(MessageCenterController* controller) {
     controller_ = controller;
@@ -106,6 +106,7 @@ class MESSAGE_CENTER_EXPORT MessageView : public views::SlideOutView {
   base::string16 accessible_name_;
 
   base::string16 display_source_;
+  bool pinned_ = false;
 
   std::unique_ptr<views::Painter> focus_painter_;