Added simplest device mount implementation (includes NullDevice and RandomDevice)

libraries/nacl-mounts/dev/Device.h

+/*
+ * 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_DEVICE_H_
+#define PACKAGES_LIBRARIES_NACL_MOUNTS_DEV_DEVICE_H_
+
+// Device
+class Device {
+ public:
+  Device() {}
+  virtual ~Device() {}
+  virtual int Read(off_t offset, void *buf, size_t count) = 0;
+  virtual int Write(off_t offset, const void *buf, size_t count) = 0;
+ private:
+  DISALLOW_COPY_AND_ASSIGN(Device);
+};
+
+#endif
+