Link MediaSessionTabHelper with native MediaSession [CL is going to be split]

content/browser/media/session/media_session_observer.cc

Index: content/browser/media/session/media_session_observer.cc
diff --git a/content/browser/media/session/media_session_observer.cc b/content/browser/media/session/media_session_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..efe1703bc72ad9b812fd898731e42c5953014761
--- /dev/null
+++ b/content/browser/media/session/media_session_observer.cc
@@ -0,0 +1,21 @@
+// 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.
+
+#include "content/browser/media/session/media_session_observer.h"
+
+#include "content/browser/media/session/media_session.h"
+
+namespace content {
+
+MediaSessionObserver::MediaSessionObserver(MediaSession* session)
+    : session_(session) {
+  session->AddObserver(this);
+}
+
+MediaSessionObserver::~MediaSessionObserver() {
+  if (session_)
+    session_->RemoveObserver(this);
+}
+
+}  // namespace content