mash: Change the MediaDelegate to a Media{Controller,Client}.

ash/public/interfaces/media.mojom

Index: ash/public/interfaces/media.mojom
diff --git a/ash/public/interfaces/media.mojom b/ash/public/interfaces/media.mojom
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+// 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;
+
+// Describes whether media is currently being captured.
+enum MediaCaptureState {
+  NONE = 0,
+  AUDIO = 1,
+  VIDEO = 2,
+  AUDIO_VIDEO = 3
+};
+
+// Allows clients (e.g. Chrome browser) to interface with the ash media
+// indicators.
+interface MediaController {
+  // Sets the client interface.
+  SetClient(associated MediaClient client);
+
+  // Called when the media capture state changes on the client, or in response
+  // to a RequestCaptureState() request. Returns an array of MediaCaptureState
+  // by index of the shell content. (These indexes are unstable, but are
+  // unlikely to change in practice, see comments in chrome's MediaClient::
+  // RequestCaptureState()).
+  NotifyCaptureState(array<MediaCaptureState> state);
+};
+
+// This delegate allows the UI code in ash to forward UI commands.
+interface MediaClient {
+  // Handles the Next Track Media shortcut key.
+  HandleMediaNextTrack();
+
+  // Handles the Play/Pause Toggle Media shortcut key.
+  HandleMediaPlayPause();
+
+  // Handles the Previous Track Media shortcut key.
+  HandleMediaPrevTrack();
+
+  // Requests that the client resends the NotifyMediaCaptureChanged() message.
+  RequestCaptureState();
+};