createIconDom_() {
    const iconImg = document.createElement('img');
    iconImg.src = './logo_only.svg';
    iconImg.alt = 'Blockly Logo';
    iconImg.width = '25';
    iconImg.height = '25';
    return iconImg;
  }
Creates the dom used for the icon.
@returns {HTMLElement} The element for the icon.
@override