Fixing a bug with poping up enlarged image when mouse is out of the thumbnail.

chrome/browser/resources/file_manager/css/file_manager.css

 /*
  * Copyright (c) 2011 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;
@@ skipping 310 matching lines @@
   -webkit-box-shadow: 2px 2px 6px rgba(0, 0, 0, 0.2);
   background-color: #F2F2F2;
 }
 
 .preview-thumbnails > div > div.popup {
   border: 2px solid #fff;
   -webkit-box-shadow: 3px 3px 9px rgba(0, 0, 0, 0.6);
   background-color: #F2F2F2;
   margin: 0;
   z-index: 1;
+  pointer-events: none;
   position: absolute;
 
   -webkit-transition: all 180ms ease-in;
   -webkit-transition-delay: 300ms;
 
   -webkit-transform: translate(0, 3px) scale(0.95);
   opacity: 0;
 }
 
 .preview-thumbnails > div:hover > div.popup {
   -webkit-transform: translate(0, 0) scale(1.0);
   opacity: 1;
+  pointer-events: auto;
 }
 
 .preview-panel > * {
   display: -webkit-box;
   -webkit-box-align: center;
 }
 
 /* cr.ui.Table has a black focus border by default, which we don't want. */
 .detail-table:focus {
   border: 0;
@@ skipping 266 matching lines @@
 /* Overlay pane covering the entire file manager window (e.g. image editor)*/
 .overlay-pane {
   position: absolute;
   top: 0;
   left: 0;
   width: 100%;
   height: 100%;
   border: none;
   z-index: 100;
 }