RELNOTES: Fix 'undefined' streaming response header in testing XhrIo.
RELNOTES: Fix 'undefined' streaming response header in testing XhrIo.

PiperOrigin-RevId: 371207002
Change-Id: I4d1b802d0172fdfaec1b8a71bbfc1f9978bc3605

google/closure-library,google/closure-library,google/closure-library,google/closure-library,google/closure-library