Avoid loading the chime when the hotword background page is opened.

chrome/browser/resources/hotword/state_manager.js

 // 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.
 
 cr.define('hotword', function() {
   'use strict';
 
   /**
    * Trivial container class for session information.
    * @param {!hotword.constants.SessionSource} source Source of the hotword
@@ skipping 88 matching lines @@
      * This is tracked separately from hotwordStatus_ because we need to restart
      * the hotword detector when this value changes.
      * @private {boolean}
      */
     this.loggingEnabled_ = false;
 
     // Get the initial status.
     chrome.hotwordPrivate.getStatus(this.handleStatus_.bind(this));
 
     // Setup the chime and insert into the page.
+    // Set preload=none to prevent an audio output stream from being created
+    // when the extension loads.
+    this.chime_.preload = 'none';
     this.chime_.src = chrome.extension.getURL(
         hotword.constants.SHARED_MODULE_ROOT + '/audio/chime.wav');
     document.body.appendChild(this.chime_);
   }
 
   /**
    * @enum {number}
    * @private
    */
   StateManager.State_ = {
@@ skipping 350 matching lines @@
 
       if (oldLocked != this.isLocked_)
         this.updateStateFromStatus_();
     }
   };
 
   return {
     StateManager: StateManager
   };
 });