Added simplest device mount implementation (includes NullDevice and RandomDevice)

libraries/nacl-mounts/dev/NullDevice.h

Index: libraries/nacl-mounts/dev/NullDevice.h
===================================================================
--- libraries/nacl-mounts/dev/NullDevice.h	(revision 0)
+++ libraries/nacl-mounts/dev/NullDevice.h	(revision 0)
@@ -0,0 +1,23 @@
+/*
+ * 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.
+ */
+#ifndef PACKAGES_LIBRARIES_NACL_MOUNTS_DEV_NULLDEVICE_H_
+#define PACKAGES_LIBRARIES_NACL_MOUNTS_DEV_NULLDEVICE_H_
+
+#include "../dev/Device.h"
+
+// NullDevice
+class NullDevice : public Device {
+ public:
+  NullDevice() {}
+  ~NullDevice() {}
+  int Read(off_t offset, void *buf, size_t count);
+  int Write(off_t offset, const void *buf, size_t count);
+ private:
+  DISALLOW_COPY_AND_ASSIGN(NullDevice);
+};
+
+#endif
+