NOT FOR LANDING Introduce and use WebMediaSession

Source/modules/mediasession/MediaSessionError.h

+// 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.
+
+#ifndef MediaSessionError_h
+#define MediaSessionError_h
+
+#include "platform/heap/Handle.h"
+#include "public/platform/modules/mediasession/WebMediaSessionError.h"
+#include <v8/include/v8.h>
+
+namespace blink {
+
+class DOMException;
+class ScriptPromiseResolver;
+
+class MediaSessionError {
+    STATIC_ONLY(MediaSessionError);
+public:
+    // For CallbackPromiseAdapter
+    using WebType = const WebMediaSessionError&;
+    static v8::Local<v8::Value> take(ScriptPromiseResolver*, const WebMediaSessionError& webError);
+};
+
+} // namespace blink
+
+#endif // MediaSessionError_h
+