Prevent dragging in open/save dialogs.

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. */
 
 /* Outer frame of the dialog. */
 body {
    -webkit-box-flex: 1;
    -webkit-box-orient: vertical;
    -webkit-transition: opacity 70ms linear;
    -webkit-user-select: none;
@@ skipping 684 matching lines @@
 }
 
 /* Text box used for renaming in the thumbnail list. */
 .thumbnail-grid input.rename {
   -webkit-box-sizing: border-box;
   -webkit-margin-start: -1px;
   height: 20px;
   width: 114px;
 }
 
-.thumbnail-grid li,
-.detail-table list li {
-  -webkit-user-drag: element;
-}
-
 /* The cr.ui.Table representing the detailed file list. */
 .detail-table {
   border: 0;
   width: 100%;
 }
 
 /* Bottom pane describing current selection. */
 .preview-panel {
   -webkit-box-align: center;
   -webkit-box-orient: horizontal;
@@ skipping 499 matching lines @@
 }
 
 body[ash] .dialog-title,
 body[type='full-page'] [invisibleif='full-page'],
 body:not([type='full-page']) [visibleif='full-page'],
 body:not([type='saveas-file']) [visibleif='saveas-file'],
 body:not([type='saveas-file']):not([type='full-page'])
     [visibleif='saveas-file full-page'] {
   display: none;
 }