Enabled Mosaic view on each volume.

chrome/browser/resources/file_manager/css/photo_import.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. */
 
 .photo-import {
   -webkit-user-select: none;
   bottom: 0;
   font-family: Noto Sans UI, Droid Sans Fallback, sans-serif;
   font-size: 84%;
   left: 0;
@@ skipping 144 matching lines @@
   -webkit-animation: fadeIn ease-in 1;
   -webkit-animation-duration: 100ms;
   -webkit-animation-fill-mode: forwards;
 }
 
 @-webkit-keyframes fadeIn {
   from {
     opacity: 0;
   }
   to {
-    opacity :1;
+    opacity: 1;
   }
 }
 
 .grid-item[lead] {
   border: 2px solid transparent !important;
 }
 
 .grid-item[selected],
 .grid-item[lead][selected],
 .grid-item:hover {
@@ skipping 59 matching lines @@
   font-size: 90%;
   min-height: 26px;
   min-width: 87px;
   position: absolute;
   right: 10px;
 }
 
 .importing-dialog .progress-bar {
   -webkit-box-flex: 1;
 }