Hide the CC button for <audio> with <track>s

Source/core/css/mediaControls.css

 /*
  * Copyright (C) 2009 Apple Inc.  All rights reserved.
  * Copyright (C) 2009 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 263 matching lines @@
     color: inherit;
 }
 
 audio::-webkit-media-controls-return-to-realtime-button, video::-webkit-media-controls-return-to-realtime-button {
     display: none;
     background-color: initial;
     border: initial;
     color: inherit;
 }
 
-audio::-webkit-media-controls-toggle-closed-captions-button, video::-webkit-media-controls-toggle-closed-captions-button {
+audio::-webkit-media-controls-toggle-closed-captions-button {
+    display: none;
+}
+
+video::-webkit-media-controls-toggle-closed-captions-button {
     -webkit-appearance: media-toggle-closed-captions-button;
     display: flex;
     flex: none;
     border: none;
     box-sizing: border-box;
     width: 30px;
     height: 30px;
     line-height: 30px;
     margin-left: -5px;
     margin-right: 9px;
@@ skipping 91 matching lines @@
     font-weight: bold;
 }
 
 video::-webkit-media-text-track-container u {
     text-decoration: underline;
 }
 
 video::-webkit-media-text-track-container i {
     font-style: italic;
 }