[MediaSession] Don't reset metadata and actions when the session goes uncontrollable

content/browser/media/session/mock_media_session_observer.cc

Index: content/browser/media/session/mock_media_session_observer.cc
diff --git a/content/browser/media/session/mock_media_session_observer.cc b/content/browser/media/session/mock_media_session_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..471e84851d87a79f36f083e67adec5d8084e5037
--- /dev/null
+++ b/content/browser/media/session/mock_media_session_observer.cc
@@ -0,0 +1,14 @@
+// Copyright 2017 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/mock_media_session_observer.h"
+
+namespace content {
+
+MockMediaSessionObserver::MockMediaSessionObserver(MediaSession* media_session)
+    : MediaSessionObserver(media_session) {}
+
+MockMediaSessionObserver::~MockMediaSessionObserver() = default;
+
+}  // content