[WebSocket] Merge duplicated HTTP headers for devtools

LayoutTests/http/tests/websocket/duplicated-headers_wsh.py

 from mod_pywebsocket import handshake
 from mod_pywebsocket.handshake.hybi import compute_accept
 
 
 def web_socket_do_extra_handshake(request):
     message = 'HTTP/1.1 101 Switching Protocols\r\n'
     message += 'Upgrade: websocket\r\n'
     message += 'Connection: Upgrade\r\n'
     message += 'Sec-WebSocket-Accept: %s\r\n' % compute_accept(request.headers_in['Sec-WebSocket-Key'])[0]
-    message += 'Sec-WebSocket-Extensions: x-foo\r\n'
+    message += 'foo: bar, baz\r\n'
+    message += 'foo: hoge\r\n'
+    message += 'FOO: FUGA\r\n'
+    message += 'xxx: yyy\r\n'
     message += '\r\n'
     request.connection.write(message)
     raise handshake.AbortedByUserException('Abort the connection') # Prevents pywebsocket from sending its own handshake message.
 
 
 def web_socket_transfer_data(request):
     pass
+