[filemanager] HiDPI icon for filemanager.

chrome/browser/resources/file_manager/css/action_choice.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. */
 
 .action-choice {
   -webkit-box-align: center;
   -webkit-box-orient: vertical;
   -webkit-user-select: none;
   background: white;
   bottom: 0;
@@ skipping 78 matching lines @@
 }
 
 .choices label[for=import-photos-to-drive] {
   background: -webkit-image-set(
     url('chrome://theme/IDR_FILE_MANAGER_IMG_FILETYPE_DRIVE') 1x,
     url('chrome://theme/IDR_FILE_MANAGER_IMG_FILETYPE_DRIVE@2x') 2x) no-repeat;
   padding-left: 20px;
 }
 
 .choices label[for=view-files] {
-  background: url(../images/icon16.png) no-repeat;
+  background: -webkit-image-set(
+    url('../images/icon16.png') 1x,
+    url('../images/icon32.png') 2x) no-repeat;
   padding-left: 20px;
 }
 
 .choices label[for=watch-single-video] {
   background: -webkit-image-set(
     url('chrome://theme/IDR_FILE_MANAGER_IMG_FILETYPE_VIDEO') 1x,
     url('chrome://theme/IDR_FILE_MANAGER_IMG_FILETYPE_VIDEO@2x') 2x) no-repeat;
   padding-left: 20px;
 }
 
 .footer {
   -webkit-box-orient: horizontal;
   -webkit-box-pack: end;
   bottom: 10px;
   display: -webkit-box;
   left: 10px;
   padding-bottom: 5px;
   position: absolute;
   right: 10px;
 }
 
 .footer button {
   height: 24px;
   margin-left: 10px;
   min-width: 80px;
 }