Make //content responsible for generating notification Ids

chrome/browser/notifications/message_center_display_service.h

Index: chrome/browser/notifications/message_center_display_service.h
diff --git a/chrome/browser/notifications/message_center_display_service.h b/chrome/browser/notifications/message_center_display_service.h
index 83ba314e9d6ee0865cfe37461486285014c5c4c4..05a8fc377d6344c0d2f4a9326a968fe611e8fea1 100644
--- a/chrome/browser/notifications/message_center_display_service.h
+++ b/chrome/browser/notifications/message_center_display_service.h
@@ -28,7 +28,6 @@ class MessageCenterDisplayService : public NotificationDisplayService {
   void Close(NotificationCommon::Type notification_type,
              const std::string& notification_id) override;
   bool GetDisplayed(std::set<std::string>* notifications) const override;
-  bool SupportsNotificationCenter() const override;
 
  private:
   Profile* profile_;