ui/file_manager/file_manager/foreground/css/combobutton.css

/* Copyright (c) 2012 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. */

.buttonbar button.combobutton {
  -webkit-box-align: stretch;
  display: -webkit-box;
}

.buttonbar .combobutton > .action {
  background-position: left center;
  background-repeat: no-repeat;
  background-size: 16px 16px;
  padding-left: 21px;
}

.buttonbar .combobutton > .trigger {
  border-left: solid 1px #dcdcdc;
  margin-left: 8px;
  margin-right: -8px;
  width: 22px;
}

/* This pseudo element expands clickable area of the .trigger */
.buttonbar .combobutton > .trigger::before {
  content: '';
  display: block;
  height: 31px;
  position: absolute;
  top: -5px;
  width: 30px;
}

.buttonbar .combobutton:not([multiple]) > .trigger {
  display: none;
}

.buttonbar .combobutton > div > span.disclosureindicator {
  -webkit-transform: rotate(90deg);
}

.buttonbar .combobutton[hidden] {
  display: none;
}