title: Javascript Controlling Audio Tag in Background.html in a Chrome Extension
body: <p>I would like to control the volume of an audio tag in a background page in a Chrome extension.
  The media plays well but at a volume by default (I think it's 1 => max) however I can change the volume.</p>
  
  <p>Do you know how to ?</p>
  
  <p><em>Background.html:</em></p>
  
  <pre><code>&lt;!doctype html&gt;
  &lt;html&gt;
  &lt;head&gt;
  &lt;/head&gt;
  &lt;body&gt;
      &lt;audio src="http://radio-contact.ice.infomaniak.ch/radio-contact-high.mp3" id="radio" 
      autoplay="true" oncanplay="document.getElementById('radio').volume = 0.1"&gt;
      &lt;/audio&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>Moreover, I want to have Pause/Volume+/Volume- buttons in a popup.html to control it. 
  I tried with chrome.extension.getBackgroundPage() but I can't control it. </p>
  
  <p>Thanks</p>