Hi Zhang
Can you confirm that this will not be the case when SharePoint 2013 has been deployed and the site collection upgrade has taken place, as we will be able to use the Powershell commands detailed in TechNet.:- technet.microsoft.com/.../fp161397.aspx.
The example of the master page was used because it is not code and therefore you cannot add debugging code.
I will submit the feedback as you suggested.
Regards
Nigel