title: Icons on contextMenu submenus in Chrome extension
body: <p>I've got a working Chrome extension that adds an item to the context menu when right-clicking on an editable field.  I'm able to add an icon to my new top-level menu item, but I can't find a way to add icons to each of my submenu items. </p>
  
  <p>You can see a screenshot of the menu here: <a href="https://lh5.googleusercontent.com/5mRSIYNceNWZyUhUUZLdvMQC2ns9LDFMWwZFEmsx37Hop4YCe9dzmS2zQCdSoUOcAmaZqvup=s640-h400-e365" rel="nofollow">https://lh5.googleusercontent.com/5mRSIYNceNWZyUhUUZLdvMQC2ns9LDFMWwZFEmsx37Hop4YCe9dzmS2zQCdSoUOcAmaZqvup=s640-h400-e365</a></p>
  
  <p>As you can see, to top-level item "GTZCode" has an icon, but all the items in that menu do not  have icons.  Is it possible to add icons to them?</p>