chrome/browser/resources/settings/settings_ui/settings_ui.html

    <style include="cr-page-host-style settings-shared">
      :host {
        display: flex;
        flex-direction: column;
        height: 100%;
        --settings-menu-width: 250px;
        /* Centered cards has a max-width of var(--cr-centered-card-max-width)
         * and a width of a certain percentage. Therefore, to make room for the
         * cards to be at their max width, the flex-basis of #main needs to be
         * whatever value the percentage of would equal to the max width. */
        --settings-main-basis: calc(var(--cr-centered-card-max-width) /
            var(--cr-centered-card-width-percentage));
      }

      cr-toolbar {
        min-height: 56px;
        --cr-toolbar-center-basis: var(--settings-main-basis);
      }

      cr-toolbar:not([narrow]) {
        --cr-toolbar-left-spacer-width: var(--settings-menu-width);
      }

      @media (prefers-color-scheme: light) {
        cr-toolbar {
          --iron-icon-fill-color: white;
        }
      }

      #cr-container-shadow-top {
        /* Needs to be higher than #container's z-index to appear above
         * scrollbars. */
        z-index: 2;
      }

      #container {
        /* CrContainerShadowMixin creates a div inside of #container to
         * calculate when the div is off-screen, indicating that the user has
         * scrolled #container. Since this div needs to be at the top of
         * #container, set align-items to flex-start. Otherwise, the flex layout
         * will stretch the div across the entire height of #container and never
         * appear off-screen. */
        align-items: flex-start;
        display: flex;
        flex: 1;
        overflow: overlay;
        position: relative;
      }

      #left,
      #main,
      #right {
        flex: 1 1 0;
      }

      #left {
        height: 100%;
        position: sticky;
        top: 0;
      }

      #left settings-menu {
        max-height: 100%;
        overflow: auto;
        overscroll-behavior: contain;
        width: var(--settings-menu-width);
      }

      #main {
        flex-basis: var(--settings-main-basis);
      }

      /* The breakpoint of 980px was decided on by the rounded sum of
       * var(--settings-main-basis), var(--settings-menu-width), and
       * var(--cr-section-padding). */
      @media (max-width: 980px) {
        #main {
          min-width: auto;
          /* Add some padding to make room for borders and to prevent focus
           * indicators from being cropped. */
          padding: 0 3px;
        }
      }
    </style>
    <settings-prefs id="prefs" prefs="{{prefs}}"></settings-prefs>
    <cr-toolbar id="toolbar"
        page-name="$i18n{settings}"
        clear-label="$i18n{clearSearch}"
        autofocus
        search-prompt="$i18n{searchPrompt}"
        on-cr-toolbar-menu-click="onMenuButtonClick_"
        spinner-active="[[toolbarSpinnerActive_]]"
        menu-label="$i18n{menuButtonLabel}"
        on-search-changed="onSearchChanged_"
        role="banner"
        narrow="{{narrow_}}"
        narrow-threshold="980"
        show-menu="[[narrow_]]">
    </cr-toolbar>
    <cr-drawer id="drawer" on-close="onMenuClose_" heading="$i18n{settings}"
        align="$i18n{textdirection}">
      <div slot="body">
        <template is="dom-if" id="drawerTemplate">
          <settings-menu id="drawerMenu"
              page-visibility="[[pageVisibility_]]"
              on-iron-activate="onIronActivate_">
          </settings-menu>
        </template>
      </div>
    </cr-drawer>
    <div id="container" class="no-outline">
      <div id="left" hidden$="[[narrow_]]">
        <settings-menu id="leftMenu"
            page-visibility="[[pageVisibility_]]"
            on-iron-activate="onIronActivate_">
        </settings-menu>
      </div>
      <settings-main id="main" prefs="{{prefs}}"
          toolbar-spinner-active="{{toolbarSpinnerActive_}}"
          page-visibility="[[pageVisibility_]]">
      </settings-main>
      <!-- An additional child of the flex #container to take up space,
           aligned with the right-hand child of the flex toolbar. -->
      <div id="right" hidden$="[[narrow_]]"></div>
    </div>