title: Can the icon of a context menu item of a Firefox web extension be changed on the fly?
body: <p>I developed a web extension for Firefox with <code>manifest.json</code> containing:</p>
  
  <pre class="lang-json prettyprint-override"><code>    "icons": {
          "16": "Open In New.svg"
      },
  </code></pre>
  
  <p>and the <code>background.js</code> containing:</p>
  
  <pre class="lang-js prettyprint-override"><code>browser.menus.create( {
    id: 'myContextMenuItem',
    title: browser.i18n.getMessage('contextMenuItemLabel'),
    contexts: ['link']
  } )
  </code></pre>
  
  <p>The icon declared in <code>manifest.json</code> is the extension's icon and is also used in front of the context menu item label. Can the latter be changed programmatically on the fly?</p>
  
  <p>I found <a href="https://stackoverflow.com/q/9499620/1744774">Change Context Menu Icon</a> but that has no answer with a solution.</p>