Add User-Agent header in opening handshake headers.
https://bugs.webkit.org/show_bug.cgi?id=110601

Reviewed by Alexey Proskuryakov.

RFC-6455 doesn't require to send User-Agent header, but allow it.
Many web application developers want to have it, and Firefox already
did it. This patch adds User-Agent header in opening handshake also in
WebKit ports.

Test: http/tests/websocket/tests/hybi/useragent-in-openinghandshake.html

Source/WebCore:

* Modules/websockets/WebSocketHandshake.cpp:
(WebCore::WebSocketHandshake::clientHandshakeMessage):
(WebCore::WebSocketHandshake::clientHandshakeRequest):

LayoutTests:

* http/tests/websocket/tests/hybi/sendback_ua_wsh.py: Added.
(web_socket_do_extra_handshake):
(web_socket_transfer_data):
* http/tests/websocket/tests/hybi/useragent-in-openinghandshake-expected.txt: Added.
* http/tests/websocket/tests/hybi/useragent-in-openinghandshake.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144037 268f45cc-cd09-0410-ab3c-d52691b4dbfc