Websites/perf.webkit.org/public/v3/components/close-button.js

class CloseButton extends ButtonBase {
    constructor()
    {
        super('close-button');
    }

    static buttonContent()
    {
        return `<g stroke="black" stroke-width="10">
            <circle cx="50" cy="50" r="45" fill="transparent"/>
            <polygon points="30,30 70,70" />
            <polygon points="30,70 70,30" />
        </g>`;
    }
}

ComponentBase.defineElement('close-button', CloseButton);