Add the supporting code for the cast system tray integration

ash/system/cast/cast_observer.h

Index: ash/system/cast/cast_observer.h
diff --git a/ash/system/cast/cast_observer.h b/ash/system/cast/cast_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..0995e158214ce2fb55933c708f94953e0f505b0f
--- /dev/null
+++ b/ash/system/cast/cast_observer.h
@@ -0,0 +1,19 @@
+// Copyright 2015 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 ASH_SYSTEM_CAST_CAST_OBSERVER_H_
+#define ASH_SYSTEM_CAST_CAST_OBSERVER_H_
+
+namespace ash {
+
+class CastObserver {

[achuithb, 2015/05/06 00:45:57]

Is this used for anything?

+ public:
+  virtual ~CastObserver() {}
+
+  virtual void OnCastRefresh() = 0;
+};
+
+}  // namespace ash
+
+#endif  // ASH_SYSTEM_CAST_CAST_OBSERVER_H_