chrome/browser/resources/chromeos/login/hd-iron-icon.css

/* Copyright 2016 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. */

@media all and (-webkit-max-device-pixel-ratio: 1.5) {
  #icon2x {
    display: none;
  }
}

@media all and (-webkit-min-device-pixel-ratio: 1.5) {
  #icon1x {
    display: none;
  }
}