chrome/browser/resources/md_extensions/shared_style.html

<link rel="import" href="chrome://resources/cr_elements/shared_vars_css.html">

<dom-module id="shared-style">
  <template>
    <style include="cr-shared-style">
      .page-container {
        height: 100%;
        overflow: overlay;
      }

      .page-content {
        @apply --cr-card-elevation;
        background-color: white;
        box-sizing: border-box;
        margin: auto;
        min-height: 100%;
        padding-bottom: 64px;
        width: var(--cr-toolbar-field-width);
      }

      .page-header {
        align-items: center;
        display: flex;
        height: 40px;
        margin-bottom: 12px;
        padding: 8px 12px 0;
      }
    </style>
  </template>
</dom-module>