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

content/browser/media/session/mock_media_session_observer.h

Index: content/browser/media/session/mock_media_session_observer.h
diff --git a/content/browser/media/session/mock_media_session_observer.h b/content/browser/media/session/mock_media_session_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..25db18dffb9d5bdcec540ff5d70825c5838aaa94
--- /dev/null
+++ b/content/browser/media/session/mock_media_session_observer.h
@@ -0,0 +1,23 @@
+// 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/public/browser/media_session_observer.h"
+#include "testing/gmock/include/gmock/gmock.h"
+
+namespace content {
+
+class MockMediaSessionObserver : public MediaSessionObserver {
+ public:
+  MockMediaSessionObserver(MediaSession* media_session);
+  virtual ~MockMediaSessionObserver() override;
+
+  MOCK_METHOD0(MediaSessionDestroyed, void());
+  MOCK_METHOD2(MediaSessionStateChanged,
+               void(bool is_controllable, bool is_suspended));
+  MOCK_METHOD1(MediaSessionMetadataChanged,
+               void(const base::Optional<MediaMetadata>& metadata));
+  MOCK_METHOD1(MediaSessionActionsChanged,
+               void(const std::set<blink::mojom::MediaSessionAction>& action));
+};
+}