Add a new GetNegotiatedProtocol method to StreamSocket and implement in all subclasses.

net/socket/socket_test_util.cc

Index: net/socket/socket_test_util.cc
diff --git a/net/socket/socket_test_util.cc b/net/socket/socket_test_util.cc
index 21eed60551dcc21345f8eb5bbec2cc5e36666cec..0e9ea78edebf3e5b0ade48d3fdf16f102a707c21 100644
--- a/net/socket/socket_test_util.cc
+++ b/net/socket/socket_test_util.cc
@@ -1166,7 +1166,7 @@ bool MockSSLClientSocket::set_was_npn_negotiated(bool negotiated) {
   return new_npn_value_ = negotiated;
 }
 
-NextProto MockSSLClientSocket::protocol_negotiated() const {
+NextProto MockSSLClientSocket::GetNegotiatedProtocol() const {
   if (is_protocol_negotiated_set_)
     return protocol_negotiated_;
   return data_->protocol_negotiated;