net: remove UsingTCPFastOpen() method from StreamSocket class

net/http/http_proxy_client_socket.cc

Index: net/http/http_proxy_client_socket.cc
diff --git a/net/http/http_proxy_client_socket.cc b/net/http/http_proxy_client_socket.cc
index a5f71073074d9d3942ddbb154e3e34960e05c8fa..5105a7001bace5b154c58dc76699469418ec7251 100644
--- a/net/http/http_proxy_client_socket.cc
+++ b/net/http/http_proxy_client_socket.cc
@@ -174,14 +174,6 @@ bool HttpProxyClientSocket::WasEverUsed() const {
   return false;
 }
 
-bool HttpProxyClientSocket::UsingTCPFastOpen() const {
-  if (transport_.get() && transport_->socket()) {
-    return transport_->socket()->UsingTCPFastOpen();
-  }
-  NOTREACHED();
-  return false;
-}
-
 bool HttpProxyClientSocket::WasNpnNegotiated() const {
   if (transport_.get() && transport_->socket()) {
     return transport_->socket()->WasNpnNegotiated();