Make downloads list keyboard shortcuts more consistent.

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. */
 
 <include src="../search_header.css">
 
 #downloads-summary-text {
   font-weight: bold;
 }
 
@@ skipping 11 matching lines @@
   padding: 0 10px 34px;
 }
 
 .download {
   -webkit-margin-start: 114px;
   -webkit-padding-start: 52px;
   margin-bottom: 15px;
   position: relative;
 }
 
+.focus-row-active {
+  background-color: rgba(0, 0, 0, .05);
+}
+
 .download,
 #no-downloads-or-results {
   margin-top: 6px;
 }
 
 .date-container {
   left: -110px;
   position: absolute;
   width: 110px;
 }
@@ skipping 101 matching lines @@
 
 .controls a {
   -webkit-margin-end: 12px;
   color: #777;
 }
 
 #downloads-pagination {
   -webkit-margin-start: 18px;
   padding-top: 24px;
 }