chrome/browser/resources/print_preview/new/throbber_css.html

<!-- Styles copied from resources/css/throbber.css. -->
<link rel="import" href="chrome://resources/html/polymer.html">

<dom-module id="throbber">
  <template>
    <style>
      .throbber {
        background: url(chrome://resources/images/throbber_small.svg) no-repeat;
        display: inline-block;
        height: 16px;
        width: 16px;
      }
    </style>
  </template>
</dom-module>