[NaCl SDK] Additional fix for r207878: Add dummy unistd.h for Windows.

native_client_sdk/src/libraries/nacl_io_test/mount_test.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 <errno.h>
 #include <fcntl.h>
 #include <string.h>
+#include <sys/stat.h>
 #include <string>
-#include <sys/stat.h>
 
+#include "gtest/gtest.h"
 #include "nacl_io/mount.h"
 #include "nacl_io/mount_dev.h"
 #include "nacl_io/mount_mem.h"
 #include "nacl_io/osdirent.h"
-
-#include "gtest/gtest.h"
+#include "nacl_io/osunistd.h"
 
 namespace {
 
 class MountMemMock : public MountMem {
  public:
   MountMemMock() {
     StringMap_t map;
     EXPECT_EQ(0, Init(1, map, NULL));
   }
 
@@ skipping 234 matching lines @@
   double expected_count = kTotalSamples / 256.;
   double chi_squared = 0;
   for (int i = 0; i < 256; ++i) {
     double difference = byte_count[i] - expected_count;
     chi_squared += difference * difference / expected_count;
   }
 
   // Approximate chi-squared value for p-value 0.05, 255 degrees-of-freedom.
   EXPECT_LE(chi_squared, 293.24);
 }