Fix gcc 4.7 building problems - cont 2.

sandbox/linux/services/libc_urandom_override.cc

 // Copyright (c) 2012 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/services/libc_urandom_override.h"
 
 #include <dlfcn.h>
 #include <pthread.h>
 #include <stdio.h>
 #include <sys/stat.h>
+#include <unistd.h>
 
 #include "base/eintr_wrapper.h"
 #include "base/logging.h"
 #include "base/rand_util.h"
 
 // Note: this file is used by the zygote and nacl_helper.
 
 namespace sandbox {
 
 // With SELinux we can carve out a precise sandbox, so we don't have to play
@@ skipping 136 matching lines @@
     CHECK(g_libc_xstat64);
     return g_libc_xstat64(version, path, buf);
   }
 }
 
 #endif  // !ADDRESS_SANITIZER
 
 #endif  // !CHROMIUM_SELINUX
 
 }  // namespace content