[Chromoting] GetHostAttributes with tests

remoting/host/host_attributes.h

+// Copyright 2016 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.
+
+#ifndef REMOTING_HOST_HOST_ATTRIBUTES_H_
+#define REMOTING_HOST_HOST_ATTRIBUTES_H_
+
+#include <string>
+
+namespace remoting {
+
+// Returns a comma-separated string to represent host attributes. The result may
+// vary if any system configurations change. So consumers should not cache the
+// result.
+// This function is thread-safe.
+std::string GetHostAttributes();
+
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_HOST_ATTRIBUTES_H_