Update from https://crrev.com/304121

sandbox/linux/syscall_broker/broker_channel.cc

+// Copyright 2014 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.
+
+#include "sandbox/linux/syscall_broker/broker_channel.h"
+
+#include <sys/socket.h>
+#include <sys/types.h>
+
+#include "base/logging.h"
+
+namespace sandbox {
+
+namespace syscall_broker {
+
+// static
+void BrokerChannel::CreatePair(EndPoint* reader, EndPoint* writer) {
+  DCHECK(reader);
+  DCHECK(writer);
+  int socket_pair[2];
+  // Use SOCK_SEQPACKET, to preserve message boundaries but we also want to be
+  // notified (recvmsg should return and not block) when the connection has
+  // been broken which could mean that the other end has been closed.
+  PCHECK(0 == socketpair(AF_UNIX, SOCK_SEQPACKET, 0, socket_pair));
+
+  reader->reset(socket_pair[0]);
+  PCHECK(0 == shutdown(reader->get(), SHUT_WR));
+
+  writer->reset(socket_pair[1]);
+  PCHECK(0 == shutdown(writer->get(), SHUT_RD));
+}
+
+}  // namespace syscall_broker
+
+}  // namespace sandbox