Add high dpi folder icons.

chrome/browser/resources/bookmark_manager/css/bmm.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. */
 
 html,
 body {
   cursor: default;
   height: 100%;
   margin: 0;
   overflow: hidden;
@@ skipping 50 matching lines @@
 html[dir=rtl] .url {
   -webkit-padding-end: 20px;
   -webkit-padding-start: 0;
 }
 
 html[dir=rtl] list .label {
   background-position: 100% 50%;
 }
 
 list > .folder > .label {
-  background-image:
-      url('../../../../../ui/resources/default_100_percent/folder_closed.png');
+  background-image: -webkit-image-set(
+      url('../../../../../ui/resources/default_100_percent/common/folder_closed.png') 1x,
+      url('../../../../../ui/resources/default_200_percent/common/folder_closed.png') 2x);
 }
 
 /* We need to ensure that even empty labels take up space */
 list > * > .label:empty:after,
 list > * > .url:empty:after {
   content: ' ';
   white-space: pre;
 }
 
 list > .folder > .url:empty:after {
@@ skipping 82 matching lines @@
   overflow: visible;
 }
 
 list [editing] .url {
   -webkit-padding-start: 10px;
 }
 
 /* end editing */
 
 html[dir=rtl] list > .folder > .label {
-  background-image: url(
-      '../../../../../ui/resources/default_100_percent/folder_closed_rtl.png');
+  background-image: -webkit-image-set(
+      url('../../../../../ui/resources/default_100_percent/common/folder_closed_rtl.png') 1x,
+      url('../../../../../ui/resources/default_200_percent/common/folder_closed_rtl.png') 2x);
 }
 
 <if expr="is_macosx">
 list > .folder > .label,
 .tree-label,
 .tree-row[may-have-children] > .tree-label,
 .tree-item[expanded] > .tree-row > .tree-label {
   background-image: -webkit-image-set(
       url('../../../../app/theme/default_100_percent/bookmark_bar_folder_mac.png') 1x,
       url('../../../../app/theme/default_200_percent/bookmark_bar_folder_mac.png') 2x);
@@ skipping 126 matching lines @@
 
 html[dir=rtl] .summary button {
   background-position: left center;
 }
 
 @media (pointer:coarse) {
   menu > button {
     line-height: 40px;
   }
 }