Adding mojo MediaSessionClient to support media controls

third_party/WebKit/public/platform/modules/mediasession/media_session.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 blink.mojom;
 
 import "mojo/common/common_custom_types.mojom";
 import "ui/gfx/geometry/mojo/geometry.mojom";
 import "url/mojo/url.mojom";
 
+// Spec: https://wicg.github.io/mediasession/
+enum MediaSessionAction {
+     PLAY,
+     PAUSE,
+     PLAY_PAUSE,
+     PREVIOUS_TRACK,
+     NEXT_TRACK,
+     SEEK_FORWARD,
+     SEEK_BACKWARD,
+     LAST = SEEK_BACKWARD

[mlamouri (slow - plz ping), 2016/10/18 17:11:14]

style: leave one empty line before "LAST" to make it more visible.

+};
+
 // Album art in MediaMetadata
 // Spec: https://wicg.github.io/mediasession/
 struct MediaImage {
   url.mojom.Url src;
   mojo.common.mojom.String16 type;
   array<gfx.mojom.Size> sizes;
 };
 
 // MediaMetadata
 // Spec: https://wicg.github.io/mediasession/
 struct MediaMetadata {
   mojo.common.mojom.String16 title;
   mojo.common.mojom.String16 artist;
   mojo.common.mojom.String16 album;
   array<MediaImage> artwork;
 };
 
+interface MediaSessionClient {
+  DidReceivedAction(MediaSessionAction action);

[whywhat, 2016/10/18 21:02:57]

nit:s/Received/Receive

+};
+
 interface MediaSessionService {
+  // MediaSessionClient interface is to used to notify Blink MediaSession of

[whywhat, 2016/10/18 21:02:57]

nit: s/to used/used/

+  // media control actions.
+  SetClient(MediaSessionClient client);
+
   SetMetadata(MediaMetadata? metadata);
+
+  EnableAction(MediaSessionAction action);
+  DisableAction(MediaSessionAction action);
 };