Implement MediaSession on top of the WebMediaPlayerDelegate.

content/common/media/media_player_delegate_messages.h

+// 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.
+
+// IPC messages for interactions between the WebMediaPlayerDelegate in the
+// renderer process and MediaWebContentsObserver in the browser process.
+// Multiply-included message file, hence no include guard.
+
+#include <stdint.h>
+
+#include "base/time/time.h"
+#include "content/common/content_export.h"
+#include "ipc/ipc_message_macros.h"
+
+#undef IPC_MESSAGE_EXPORT
+#define IPC_MESSAGE_EXPORT CONTENT_EXPORT
+#define IPC_MESSAGE_START MediaPlayerDelegateMsgStart
+
+// ----------------------------------------------------------------------------
+// Messages from the browser to the renderer requesting playback state changes.
+// ----------------------------------------------------------------------------
+
+IPC_MESSAGE_ROUTED1(MediaPlayerDelegateMsg_Pause,
+                    int /* delegate_id, distinguishes instances */)
+
+IPC_MESSAGE_ROUTED1(MediaPlayerDelegateMsg_Play,
+                    int /* delegate_id, distinguishes instances */)
+
+IPC_MESSAGE_ROUTED2(MediaPlayerDelegateMsg_UpdateVolumeMultiplier,
+                    int /* delegate_id, distinguishes instances */,
+                    double /* multiplier */)
+
+// ----------------------------------------------------------------------------
+// Messages from the renderer notifying the browser of playback state changes.
+// ----------------------------------------------------------------------------
+
+IPC_MESSAGE_ROUTED1(MediaPlayerDelegateHostMsg_OnMediaDestroyed,
+                    int /* delegate_id, distinguishes instances */)
+
+IPC_MESSAGE_ROUTED2(MediaPlayerDelegateHostMsg_OnMediaPaused,
+                    int /* delegate_id, distinguishes instances */,
+                    bool /* reached end of stream */)
+
+IPC_MESSAGE_ROUTED5(MediaPlayerDelegateHostMsg_OnMediaPlaying,
+                    int /* delegate_id, distinguishes instances */,
+                    bool /* has_video */,
+                    bool /* has_audio */,
+                    bool /* is_remote */,
+                    base::TimeDelta /* duration */)