chromium/chrome/browser/resources/password_manager/site_favicon.html

<style include="cr-hidden-style">
  :host {
    --site-favicon-height: 16px;
    --site-favicon-width: 16px;
    overflow: hidden;
  }

  #favicon,
  #downloadedFavicon {
    background-size: contain;
    height: var(--site-favicon-height);
    width: var(--site-favicon-width);
  }

  #downloadedFavicon {
    display: block;
  }
</style>
<div id="favicon" style="background-image: [[getBackgroundImage_(domain)]]"
    hidden="[[showDownloadedIcon_]]">
</div>
<img is="cr-auto-img" id="downloadedFavicon" hidden="[[!showDownloadedIcon_]]"
    on-load="onLoadSuccess_" on-error="onLoadError_" auto-src="[[url]]">