Doubling the gap between the file type combo and the Open/Cancel buttons.

chrome/browser/resources/file_manager/css/file_manager.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. */
 
 html.col-resize * {
   cursor: col-resize !important;
 }
 
 /* Outer frame of the dialog. */
 body {
@@ skipping 340 matching lines @@
 .dialog-footer[progress] #filename-input-box,
 .dialog-footer[progress] #file-type {
   display: none;
 }
 
 .dialog-footer .progress-bar {
   -webkit-margin-end: 20px;
   -webkit-margin-start: 20px;
 }
 
+#file-type {
+  -webkit-margin-end: 10px;
+}
+
 /* The container for breadcrumb elements. */
 .breadcrumbs {
   -webkit-box-align: center;
   -webkit-box-flex: 1;
   -webkit-box-orient: horizontal;
   display: -webkit-box;
   line-height: 20px;
   overflow: hidden;
   padding-top: 1px;
 }
@@ skipping 1089 matching lines @@
   height: 100%;
 }
 
 #list-container .table-header-cell:hover {
   background-color: #f2f2f2;
 }
 
 button:focus {
   outline-color: rgb(77, 144, 254);
 }