Add request attribute indicating a response is streaming

Servlet containers may need to give streaming responses special
treatment, e.g. to avoid aggressively buffering even in the presence
of flush(). Expose in a request attribute whether the request requires
a streaming response, so this can be introspected by filters.

Change-Id: If9cb6633fcbcfc5b851f097e633d3705321f007d
1 file changed