[Chromecast] Add new volume control API to CastMediaShlib

chromecast/media/base/audio_device_ids.cc

Index: chromecast/media/base/audio_device_ids.cc
diff --git a/chromecast/media/base/audio_device_ids.cc b/chromecast/media/base/audio_device_ids.cc
new file mode 100644
index 0000000000000000000000000000000000000000..af27c3da5a06f7e6cd6b760557edfe7170137528
--- /dev/null
+++ b/chromecast/media/base/audio_device_ids.cc
@@ -0,0 +1,15 @@
+// Copyright 2017 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.
+
+#include "chromecast/media/base/audio_device_ids.h"
+
+namespace chromecast {
+namespace media {
+
+const char kAlarmAudioDeviceId[] = "assistant-alarm";
+const char kTtsAudioDeviceId[] = "assistant-tts";
+const char kLocalAudioDeviceId[] = "local";
+
+}  // namespace media
+}  // namespace chromecast