Update from https://crrev.com/328418

third_party/libevent/nacl_nonsfi/signal_stub.c

+/*
+ * Copyright 2015 The Chromium Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/*
+ * In nacl_helper_nonsfi, socketpair() is unavailable. In libevent, it is used
+ * to notify of a signal handler invocation, which is unused in
+ * nacl_helper_nonsfi. Unfortunately, there is no macro to disable the feature,
+ * so we stub out the signal module entirely.
+ */
+
+
+#include <signal.h>
+#include <stdlib.h>
+#include <sys/queue.h>
+
+/* config.h must be included before any other libevent header is included. */
+#include "config.h"
+
+#include "third_party/libevent/event-internal.h"
+#include "third_party/libevent/event.h"
+#include "third_party/libevent/evsignal.h"
+
+
+struct event_base *evsignal_base = 0;
+
+int evsignal_init(struct event_base *base) {
+  /* Do nothing, and return success. */
+  return 0;
+}
+
+void evsignal_process(struct event_base *base) {
+}
+
+int evsignal_add(struct event *event) {
+  /* Do nothing, and return an error. */
+  return -1;
+}
+
+int evsignal_del(struct event *event) {
+  /* Do nothing, and return an error. */
+  return -1;
+}
+
+void evsignal_dealloc(struct event_base *base) {
+}