Reading from and writing to a cache entry simultaneously

Since I'm trying to build the implementation for bug 898524 on top of 
the new cache code, I would like to clarify something. Right now, the 
Service Worker spec only supports creating a synthesized Response object 
all at once, which means that we'll potentially have to store large 
amounts of data in memory. In the future, we're interested in 
introducing a streaming response API to ameliorate this problem - does 
the cache entry API support this? If the worker is writing data into the 
cache entry progressively, it would be best if the channel could be 
reading and processing this data at the same time. Is this possible?

Cheers,
Josh