Add WebSocketHttp2HandshakeStream.

Add WebSocketHttp2HandshakeStream class to perform handshake according
to https://tools.ietf.org/html/draft-ietf-httpbis-h2-websockets-00.

Add WebSocketHandshakeStreamBase::CreateHttp2Stream() pure virtual
method and implement it in all derived classes.

Remove lowercase WebSocket-related headers that are not used after all
(they are leftover from early days of WebSockets over SPDY).

Bug: 801564
Change-Id: I02ca36c4ce3511de7f88b977083bc2b33c3bfcc1
Reviewed-on: https://chromium-review.googlesource.com/926769
Commit-Queue: Bence Béky <bnc@chromium.org>
Reviewed-by: Adam Rice <ricea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#538522}
16 files changed