makeButton_(name, buttonStyle, callback) {
    const button = document.createElement('button');
    switch (buttonStyle) {
      case shakaDemo.Custom.ButtonStyle_.FAB: {
        button.classList.add('mdl-button--fab');
        button.classList.add('mdl-button--colored');
        const icon = document.createElement('i');
        icon.classList.add('material-icons-round');
        icon.textContent = name;
        button.appendChild(icon);
      } break;
      case shakaDemo.Custom.ButtonStyle_.RAISED:
        button.textContent = name;
        button.classList.add('mdl-button--raised');
        break;
      case shakaDemo.Custom.ButtonStyle_.PLAIN:
        button.textContent = name;
        break;
    }
    button.addEventListener('click', callback);
    button.classList.add('mdl-button');
    button.classList.add('mdl-js-button');
    button.classList.add('mdl-js-ripple-effect');
    return button;
  }
@param {string} name
@param {shakaDemo.Custom.ButtonStyle_} buttonStyle
  What style should this button be in?
@param {function()} callback
@return {!Element}
@private