Adds initial key systems support for Chromecast.

chromecast/media/base/key_systems_common.h

+// Copyright 2014 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 CHROMECAST_MEDIA_BASE_KEY_SYSTEMS_COMMON_H_
+#define CHROMECAST_MEDIA_BASE_KEY_SYSTEMS_COMMON_H_
+
+#include <string>
+
+namespace chromecast {
+namespace media {
+
+extern const char kChromecastPlayreadyKeySystem[];
+
+enum CastKeySystem {
+  KEY_SYSTEM_NONE = 0,
+  KEY_SYSTEM_CLEAR_KEY,
+  KEY_SYSTEM_PLAYREADY,
+  KEY_SYSTEM_WIDEVINE
+};
+
+// Translates a key system string into a CastKeySystem, calling into the
+// platform for known key systems if needed.

[ddorwin, 2014/09/16 18:15:00]

I think the text after the comma is incorrect based on the implementation and
function below.

[gunsch, 2014/09/16 18:55:33]

Comment was correct, fixed the implementation :)

+CastKeySystem GetKeySystemByName(const std::string& key_system_name);
+
+// Translates a platform-specific key system string into a CastKeySystem.

[ddorwin, 2014/09/16 18:15:00]

TODO: Remove when prefixed EME is removed?

[gunsch, 2014/09/16 18:55:33]

Done.

+CastKeySystem GetPlatformKeySystemByName(const std::string& key_system_name);
+
+}  // namespace media
+}  // namespace chromecast
+
+#endif  // CHROMECAST_MEDIA_BASE_KEY_SYSTEMS_COMMON_H_