Clean up HTMLTrackElement.kind invalid/missing value default handling

third_party/WebKit/Source/core/html/track/AudioTrack.h

 // Copyright 2014 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 AudioTrack_h
 #define AudioTrack_h
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/CoreExport.h"
 #include "core/html/track/TrackBase.h"
 
 namespace blink {
 
 class CORE_EXPORT AudioTrack final : public GarbageCollectedFinalized<AudioTrack>, public TrackBase, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
     USING_GARBAGE_COLLECTED_MIXIN(AudioTrack);
 public:
     static AudioTrack* create(const String& id, const AtomicString& kind, const AtomicString& label, const AtomicString& language, bool enabled)
     {
-        return new AudioTrack(id, kind, label, language, enabled);
+        return new AudioTrack(id, isValidKindKeyword(kind) ? kind : emptyAtom, label, language, enabled);
     }
 
     ~AudioTrack() override;
     DECLARE_VIRTUAL_TRACE();
 
     bool enabled() const { return m_enabled; }
     void setEnabled(bool);
 
     // Valid kind keywords.
     static const AtomicString& alternativeKeyword();
     static const AtomicString& descriptionsKeyword();
     static const AtomicString& mainKeyword();
     static const AtomicString& mainDescriptionsKeyword();
     static const AtomicString& translationKeyword();
     static const AtomicString& commentaryKeyword();
 
     static bool isValidKindKeyword(const String&);
 
 private:
     AudioTrack(const String& id, const AtomicString& kind, const AtomicString& label, const AtomicString& language, bool enabled);
 
-    // TrackBase
-    bool isValidKind(const AtomicString& kind) const override { return isValidKindKeyword(kind); }
-    AtomicString invalidValueDefaultKind() const override;
-
     bool m_enabled;
 };
 
 DEFINE_TRACK_TYPE_CASTS(AudioTrack, WebMediaPlayer::AudioTrack);
 
 } // namespace blink
 
 #endif // AudioTrack_h