Remove cookieRequestHeaderFieldValue() and setCookie() call from WebSocketHandshake

These calls were for non-Chromium port of WebKit to get/set cookies on
WebSocket opening handshake. In Blink, they're no longer necessary.
Chromium intercepts handshakes in the browser process and add/remove
cookies. Any cookie header added by Blink is ignored. Set-cookies are
stripped before forwarded to Blink.

BUG=none

Review URL: https://codereview.chromium.org/209823002

git-svn-id: svn://svn.chromium.org/blink/trunk@170560 bbb929c8-8fbe-4397-9dbb-9b2b20218538