chrome/browser/resources/ntp4/new_guest_tab_theme.css

/* Copyright 2013 The Chromium Authors. All rights reserved.
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

html {
  background-attachment: fixed;
  background-color: $2;
  background-image: url(chrome://theme/IDR_THEME_NTP_BACKGROUND?$1);
  background-position: $3;
  background-repeat: $5;
  height: 100%;
  overflow: auto;
}

#attribution-img {
  content: url(chrome://theme/IDR_THEME_NTP_ATTRIBUTION?$1);
}

html[bookmarkbarattached='true'] {
  background-position: $4;
}