Add sessions to HttpServer.

runtime/bin/crypto_macos.cc

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#include <errno.h>
+#include <fcntl.h>
+
+#include "bin/fdutils.h"
+#include "bin/crypto.h"
+
+
+bool Crypto::GetRandomBytes(intptr_t count, uint8_t* buffer) {
+  intptr_t fd = TEMP_FAILURE_RETRY(open("/dev/urandom", O_RDONLY));
+  if (fd < 0) return false;
+  intptr_t bytes_read = read(fd, buffer, count);
+  close(fd);
+  return bytes_read == count;
+}