This is a breaking change. Request: https://github.com/dart-lang/sdk/issues/33501
HttpHeaders use lowercase by default for all headers, since it is supposed to be case insensitive. Some servers incorrectly treat case as significant, however, and expect headers with capitalization or in uppercase. The current implementation forces headers to be lower cases when adding values. Users cannot even manually modify the headers.
This change removes this restriction here so that users can modify the headers to whatever form they want. The new behavior is backwards compatible except if class was implemented. All headers inside http.dart are written as lower cases, adding values to HttpHeaders is still receiving lower cases input.
The other cl (https://dart-review.googlesource.com/c/http_multi_server/+/121411) migrates multi_headers.dart to be compatible with this change.
Bug: https://github.com/dart-lang/sdk/issues/33501
Change-Id: Ieb9f4061b27ed3bbc6d82e6a408c77d11abb037b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/135357
Commit-Queue: Zichang Guo <zichangguo@google.com>
Reviewed-by: Lasse R.H. Nielsen <lrn@google.com>
d39cdf03f8