Added simplest device mount implementation (includes NullDevice and RandomDevice)

libraries/nacl-mounts/dev/RandomDevice.h

Index: libraries/nacl-mounts/dev/RandomDevice.h
===================================================================
--- libraries/nacl-mounts/dev/RandomDevice.h	(revision 0)
+++ libraries/nacl-mounts/dev/RandomDevice.h	(revision 0)
@@ -0,0 +1,26 @@
+/*
+ * 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_RANDOMDEVICE_H_
+#define PACKAGES_LIBRARIES_NACL_MOUNTS_DEV_RANDOMDEVICE_H_
+
+#include "../dev/Device.h"
+
+// RandomDevice
+class RandomDevice : public Device {
+ public:
+  RandomDevice(int (*get_random_bytes)(void *buf, size_t count, size_t *nread))
+    : get_random_bytes_(get_random_bytes) {}
+  virtual ~RandomDevice() {}
+  int Read(off_t offset, void *buf, size_t count);
+  int Write(off_t offset, const void *buf, size_t count);
+ private:
+  int (*get_random_bytes_)(void *buf, size_t count, size_t *nread);
+
+  DISALLOW_COPY_AND_ASSIGN(RandomDevice);
+};
+
+#endif
+