mash: Change CastConfigDelegate to a mojoified CastConfigClient.

ash/public/interfaces/cast_config.mojom

+// 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.
+
+module ash.mojom;
+
+struct CastSink {
+  string id;
+  string name;
+  string domain;
+};
+
+enum ContentSource {
+  UNKNOWN,
+  TAB,
+  DESKTOP
+};
+
+struct CastRoute {
+  string id;
+  string title;
+
+  // Is the activity source this computer? ie, are we mirroring the display?
+  bool is_local_source = false;
+
+  // What is source of the content? For example, we could be DIAL casting a
+  // tab or mirroring the entire desktop.
+  ContentSource content_source = ContentSource.UNKNOWN;
+};
+
+struct SinkAndRoute {
+  CastSink sink;
+  CastRoute route;
+};
+
+// Allows clients (e.g. Chrome browser) to interface with the cast item in the
+// system tray.
+interface CastConfig {
+  // Sets the client interface. This client interface will receive commands from
+  // ash and provide OnDevicesUpdated() calls.
+  SetClient(associated CastConfigClient client);
+
+  // Invoked whenever there is new sink or route information available.
+  OnDevicesUpdated(array<SinkAndRoute> device);
+};
+
+// This delegate allows the UI code in ash, e.g. |TrayCastDetailedView|,
+// to access the cast system.
+//
+// TODO(erg): Eventually, this should no longer be exported by chrome, but
+// should be exported by a separate cast service.
+interface CastConfigClient {
+  // Request fresh data from the backend. When the data is available, all
+  // registered observers will get called.
+  RequestDeviceRefresh();
+
+  // Initiate a casting session to |sink|.
+  CastToSink(CastSink sink);
+
+  // A user-initiated request to stop the given cast session.
+  StopCasting(CastRoute route);
+};