Not remove a pinned notification by user action

ui/message_center/message_center_impl.cc

Index: ui/message_center/message_center_impl.cc
diff --git a/ui/message_center/message_center_impl.cc b/ui/message_center/message_center_impl.cc
index d4b81afc9347c1d40a5df5b40e4122c4ae97c42a..de7ef42160629681cc976480c3cadff9e9815041 100644
--- a/ui/message_center/message_center_impl.cc
+++ b/ui/message_center/message_center_impl.cc
@@ -616,7 +616,11 @@ void MessageCenterImpl::RemoveNotification(const std::string& id,
 
 void MessageCenterImpl::RemoveNotificationImmediately(
     const std::string& id, bool by_user) {
-  if (FindVisibleNotificationById(id) == NULL)
+  Notification* notification = FindVisibleNotificationById(id);
+  if (notification == NULL)
+    return;
+
+  if (by_user && notification->pinned())
     return;
 
   // In many cases |id| is a reference to an existing notification instance