am 7a573862: Merge change 5720 into donut

Merge commit '7a5738624fa78e328b5f36c687c20b9cf0eb5a60'

* commit '7a5738624fa78e328b5f36c687c20b9cf0eb5a60':
  Fix #1876303. Even rfc2616 4.2 says that "Field names are case-insensitive.", servers including Google internal uses case-sensitive checking for "Cookie". So change it.