Fix alpha mask for download progress on high DPI displays.

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. */
 
 body {
   margin: 10px 10px 34px 10px;
 }
 
 .header {
   clear: both;
@@ skipping 116 matching lines @@
 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 {
   color: red;
 }
@@ skipping 17 matching lines @@
 
 .controls a {
   -webkit-margin-end: 16px;
   color: #777;
 }
 
 #downloads-pagination {
   -webkit-margin-start: 18px;
   padding-top: 24px;
 }