chromium/chrome/test/data/page_load_metrics/seamless-iframe.css

/* Copyright 2017 The Chromium Authors
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
/* To prevent an iframe from painting in the document it is hosted in, we use
 * the 'seamless' class, which prevents the frame from drawing borders or
 * scrollbars.
 */
iframe.seamless {
    border: 0px none transparent;
    overflow: hidden;
}