propose a new utility API in PartialPageUtils to complate the response

[Yuan Gao]

 hi,

I'd like to propose a new utility API to complete the PPR response.  
Talked with Blake and we suggest to put it in PartialPageUtils. Here is 
the JIRA:
https://issues.apache.org/jira/browse/TRINIDAD-2061
Please review.

Thanks,
-Yuan