Hook up RendererMediaSessionManager with browser side

content/common/media/media_session_messages_android.h

Index: content/common/media/media_session_messages_android.h
diff --git a/content/common/media/media_session_messages_android.h b/content/common/media/media_session_messages_android.h
new file mode 100644
index 0000000000000000000000000000000000000000..3ea4a7e3f6d961ea531ca8d4e4f335dbfe39bca4
--- /dev/null
+++ b/content/common/media/media_session_messages_android.h
@@ -0,0 +1,33 @@
+// 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.
+
+// IPC messages for the Media Session API.
+// Multiply-included message file, hence no include guard.
+
+#include "base/basictypes.h"
+#include "content/common/android/gin_java_bridge_errors.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 MediaSessionMsgStart
+
+// Messages for notifying the render process of media session status -------

[Mike West, 2015/12/09 17:39:59]

Tiny nit: We usually have some sort of "Messages from browser to renderer" and
"Messages from renderer to browser" for overly explicit clarity. :)

[davve, 2015/12/10 08:28:38]

Done.

+
+IPC_MESSAGE_ROUTED2(MediaSessionMsg_DidActivate,
+                    int /* request_id */,
+                    bool /* success */)
+
+IPC_MESSAGE_ROUTED1(MediaSessionMsg_DidDeactivate, int /* request_id */)
+
+// Messages for controlling the media session in browser process ----------
+
+IPC_MESSAGE_ROUTED2(MediaSessionHostMsg_Activate,
+                    int /* session_id */,
+                    int /* request_id */)
+
+IPC_MESSAGE_ROUTED2(MediaSessionHostMsg_Deactivate,
+                    int /* session_id */,
+                    int /* request_id */)