Support notifications with custom content

ui/message_center/notification_delegate.h

Index: ui/message_center/notification_delegate.h
diff --git a/ui/message_center/notification_delegate.h b/ui/message_center/notification_delegate.h
index 059a15dfda6a025b2d34ab8e3d62808596899dba..2c1a2b0a84c41d08766dd99abb35262447252b46 100644
--- a/ui/message_center/notification_delegate.h
+++ b/ui/message_center/notification_delegate.h
@@ -5,6 +5,7 @@
 #ifndef UI_MESSAGE_CENTER_NOTIFICATION_DELEGATE_H_
 #define UI_MESSAGE_CENTER_NOTIFICATION_DELEGATE_H_
 
+#include <memory>
 #include <string>
 
 #include "base/callback.h"
@@ -16,6 +17,10 @@ namespace content {
 class RenderViewHost;
 }
 
+namespace views {
+class View;
+}
+
 namespace message_center {
 
 // Delegate for a notification. This class has two roles: to implement callback
@@ -46,6 +51,10 @@ class MESSAGE_CENTER_EXPORT NotificationDelegate
   // To be called in order to detect if a settings button should be displayed.
   virtual bool ShouldDisplaySettingsButton();
 
+  // To be called to construct the contents view of a popup for notifications
+  // whose type is NOTIFICATION_TYPE_CUSTOM.
+  virtual std::unique_ptr<views::View> CreateCustomContent();
+
  protected:
   virtual ~NotificationDelegate() {}