Gather metrics classifying the cause of the TLS fallback.

net/socket/ssl_client_socket_pool.cc

Index: net/socket/ssl_client_socket_pool.cc
diff --git a/net/socket/ssl_client_socket_pool.cc b/net/socket/ssl_client_socket_pool.cc
index 11de9193e579f51958af552bf40a31eee0204148..f8db1d0504136d3f25863816e834ccc01bdd81f8 100644
--- a/net/socket/ssl_client_socket_pool.cc
+++ b/net/socket/ssl_client_socket_pool.cc
@@ -163,6 +163,8 @@ void SSLConnectJob::GetAdditionalErrorState(ClientSocketHandle* handle) {
   handle->set_ssl_error_response_info(error_response_info_);
   if (!connect_timing_.ssl_start.is_null())
     handle->set_is_ssl_error(true);
+  if (ssl_socket_)
+    handle->set_ssl_failure_state(ssl_socket_->GetSSLFailureState());
 
   handle->set_connection_attempts(connection_attempts_);
 }