Use chrome_html structure for shared_resources and options2 page.

chrome/browser/resources/downloads/downloads.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. */
 
 #downloads-summary {
   background-color: rgb(235, 239, 249);
   border-top: 1px solid rgb(156, 194, 239);
   margin-bottom: 6px;
   margin-top: 12px;
   padding: 3px;
@@ skipping 89 matching lines @@
   width: 48px;
 }
 
 html[dir=rtl] .progress {
   left: auto;
   right: 0;
 }
 
 .progress.background {
   background: url('chrome://theme/IDR_DOWNLOAD_PROGRESS_BACKGROUND_32');
+  background-size: 48px;
 }
 
 .progress.foreground {
   background: url('chrome://theme/IDR_DOWNLOAD_PROGRESS_FOREGROUND_32');
+  background-size: 48px;
 }
 
 .name {
   -webkit-padding-end: 16px;
   display: none;
   max-width: 450px;
   word-break: break-all;
 }
 
 .interrupted {
@@ skipping 19 matching lines @@
 
 .controls a {
   -webkit-margin-end: 16px;
   color: #777;
 }
 
 #downloads-pagination {
   -webkit-margin-start: 18px;
   padding-top: 24px;
 }