chromium/ash/webui/personalization_app/resources/js/wallpaper/wallpaper_subpage_element.html

<style include="common">
  #wallpaperContainer {
    display: grid;
    grid-template-areas:
      'leftspacertop    selected   rightspacertop   '
      'leftspacerbottom imagegrid  rightspacerbottom';
    grid-template-columns: minmax(10px, 1fr) minmax(568px, 920px) minmax(10px, 1fr);
    grid-template-rows: 172px minmax(0, 1fr);
    height: 100%;
    min-height: var(--personalization-app-subpage-container-min-height);
    position: relative;
    width: 100%;
  }

  wallpaper-selected {
    background-color: var(--cros-sys-app_base_shaded);
    grid-area: selected;
    position: sticky;
    top: 56px;
    z-index: 1;
  }

  wallpaper-collections,
  wallpaper-images,
  google-photos-collection,
  local-images {
    grid-area: imagegrid;
    padding: 10px 0;
    background-color: var(--cros-bg-color);
  }

  div[class$='spacertop'] {
    position: sticky;
    top: 56px;
    z-index: 1;
  }
</style>
<div id="wallpaperContainer">
  <!-- Prevent left margin from collapsing on narrow window in RTL -->
  <div class="leftspacertop"></div>
  <div class="leftspacerbottom"></div>
  <wallpaper-selected path="[[path]]" collection-id="[[queryParams.id]]"
      google-photos-album-id="[[queryParams.googlePhotosAlbumId]]"
      is-google-photos-album-shared="[[isGooglePhotosAlbumShared_]]">
  </wallpaper-selected>
  <!-- do not use hidden$ here - need to listen on property change in
          these elements. -->
  <wallpaper-collections hidden="[[!shouldShowCollections_(path)]]">
  </wallpaper-collections>
  <template is="dom-if" if="[[shouldShowCollectionImages_(path)]]" restamp>
    <wallpaper-images collection-id="[[queryParams.id]]"></wallpaper-images>
  </template>
  <template is="dom-if" if="[[shouldShowGooglePhotosCollection_(path)]]"
      restamp>
    <google-photos-collection path="[[path]]"
        album-id="[[queryParams.googlePhotosAlbumId]]">
    </google-photos-collection>
  </template>
  <template is="dom-if" if="[[shouldShowLocalCollection_(path)]]" restamp>
    <local-images></local-images>
  </template>
  <!-- Prevent the right margin from collapsing when window gets very
           narrow -->
  <div class="rightspacertop"></div>
  <div class="rightspacerbottom"></div>
</div>