Handle no volume in chrome://media-internals

chrome/browser/resources/media_internals/media_internals.js

 // Copyright (c) 2011 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 src="cache_entry.js"/>
 <include src="disjoint_range_set.js"/>
 <include src="event_list.js"/>
 <include src="item_store.js"/>
 <include src="media_player.js"/>
 <include src="metrics.js"/>
@@ skipping 23 matching lines @@
   var audioStreamDiv;
   var cacheDiv;
 
   // A timer used to limit the rate of redrawing the Media Players section.
   var redrawTimer = null;
 
   /**
    * Initialize variables and ask MediaInternals for all its data.
    */
   function initialize() {
-    audioStreamDiv = document.getElementById('audio-streams');
-    cacheDiv = document.getElementById('cache-entries');
+    audioStreamDiv = $('audio-streams');
+    cacheDiv = $('cache-entries');
 
     // Get information about all currently active media.
     chrome.send('getEverything');
   }
 
   /**
    * Write the set of audio streams to the DOM.
    */
   function printAudioStreams() {
 
     /**
      * Render a single stream as a <li>.
      * @param {Object} stream The stream to render.
      * @return {HTMLElement} A <li> containing the stream information.
      */
     function printStream(stream) {
       var out = document.createElement('li');
       out.id = stream.id;
       out.className = 'audio-stream';
       out.setAttribute('status', stream.status);
 
       out.textContent += 'Audio stream ' + stream.id.split('.')[1];
       out.textContent += ' is ' + (stream.playing ? 'playing' : 'paused');
-      out.textContent += ' at ' + (stream.volume * 100).toFixed(0);
-      out.textContent += '% volume.';
+      if (typeof stream.volume != 'undefined') {
+        out.textContent += ' at ' + (stream.volume * 100).toFixed(0);
+        out.textContent += '% volume.';
+      }
       return out;
     }
 
     var out = document.createElement('ul');
     audioStreams.map(printStream).forEach(function(s) {
-      out.appendChild(s)
+      out.appendChild(s);
     });
 
     audioStreamDiv.textContent = '';
     audioStreamDiv.appendChild(out);
   }
 
   /**
    * Redraw each MediaPlayer.
    */
   function printMediaPlayers() {
@@ skipping 53 matching lines @@
     }
   }
 
   /**
    * A render process has ended, delete any media players associated with it.
    * @param {number} renderer The id of the render process.
    */
   function onRendererTerminated(renderer) {
     for (var key in mediaPlayers) {
       if (mediaPlayers[key].renderer == renderer) {
-        document.getElementById('media-players').removeChild(mediaPlayers[key]);
+        $('media-players').removeChild(mediaPlayers[key]);
         delete mediaPlayers[key];
         break;
       }
     }
     printMediaPlayers();
   }
 
   /**
    * Receiving net events.
    * Update cache information and update that section of the page.
@@ skipping 109 matching lines @@
     onMediaEvent: onMediaEvent
   };
 });
 
 /**
  * Initialize everything once we have access to the DOM.
  */
 document.addEventListener('DOMContentLoaded', function() {
   media.initialize();
 });