[Files.app] Fix the z-indexes of special elements (2)

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. */
 
+/* The order of z-index:
+ * - 2: drag-selection-bodrder
+ * - 3: preview-panel
+ * - 500: scrollbar
+ * - 500: splitter
+ * - 550: autocomplete-suggestions
+ * - 600: menus
+ * - 600: tooltip
+ * - 1000: preview thumbnail popup
+ * - 1000: overlay panel (ie. image editor)
+ */
+
 /* Special attribute used in HTML to hide elements. */
 body[type='folder'] [invisibleif~='folder'],
 body[type='upload-folder'] [invisibleif~='upload-folder'],
 body[type='saveas-file'] [invisibleif~='saveas-file'],
 body[type='open-file'] [invisibleif~='open-file'],
 body[type='open-multi-file'] [invisibleif~='open-multi-file'],
 body[type='full-page'] [invisibleif~='full-page'],
 
 body[type='folder'] [visibleif]:not([visibleif~='folder']),
 body[type='upload-folder'] [visibleif]:not([visibleif~='upload-folder']),
@@ skipping 1115 matching lines @@
   -webkit-transform: translate(0, 3px) scale(0.95);
   background-color: #f2f2f2;
   border: 2px solid #fff;
   box-shadow: 0 0 0 1px #F0F0F0,
               0 0 0 2px #D0D0D0,
               2px 2px 6px rgba(0, 0, 0, 0.2);
   margin: 6px 0 0 -40px;
   opacity: 0;
   pointer-events: none;
   position: absolute;
-  z-index: 1;
+  z-index: 1;  /* will be overridden with 1000 by script. */
 }
 
 .preview-thumbnails > .popup > img {
   -webkit-user-drag: none;
 }
 
 .preview-thumbnails > * {
   transition: all 180ms ease-in;
   transition-delay: 300ms;
 }
@@ skipping 594 matching lines @@
   background-color: rgb(250, 250, 250);
   border: 1px solid rgb(255, 255, 255);
   border-radius: 3px;
   box-shadow: 0 1px 4px 0 rgba(0, 0, 0, .5);
   box-sizing: border-box;  /* To match the width with the search box's. */
   color: rgb(34, 34, 34);
   overflow: hidden;
   padding: 5px 0;
   position: fixed;
   width: 300px !important; /* This overrides the value specified by script. */
-  z-index: 3;
+  z-index: 550;
 }
 
 list.autocomplete-suggestions > li {
   -webkit-box-align: center;
   display: -webkit-box;
   padding: 3px 0;
 }
 
 list.autocomplete-suggestions > li > div.detail-icon {
   -webkit-margin-end: 6px;
@@ skipping 180 matching lines @@
 }
 
 .share-dialog-webview-wrapper:not(.loaded) .share-dialog-webview {
   visibility: hidden;
 }
 
 .share-dialog-frame .cr-dialog-text,
 .share-dialog-frame .cr-dialog-buttons {
   display: none;
 }