Added simplest device mount implementation (includes NullDevice and RandomDevice)

libraries/nacl-mounts/test.nacl/DevTest.cc

+/*
+ * Copyright (c) 2012 The Native Client 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 "../base/KernelProxy.h"
+#include "gtest/gtest.h"
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+TEST(DevTest, Simple) {
+  struct stat buf;
+  EXPECT_EQ(0, stat("/dev/random", &buf));
+  int h = open("/dev/random", O_RDONLY);
+  EXPECT_GT(h, 0);
+  char buff[5];
+  EXPECT_EQ(5, read(h, reinterpret_cast<void*>(buff), 5));
+  int q = open("/dev/null", O_WRONLY);
+  EXPECT_EQ(5, write(q, reinterpret_cast<void*>(buff), 5));
+  EXPECT_EQ(0, read(q, reinterpret_cast<void*>(buff), 5));
+}