Fixed close button for retina displays in identity approval scope UI

chrome/browser/resources/identity_scope_approval_dialog/scope_approval_dialog.css

 /* Copyright (c) 2013 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: 0;
   padding: 0;
 }
 
 .titlebar {
   -webkit-app-region: drag;
   background-color: white;
   height: 26px;
   white-space: nowrap;
   width: 100%;
 }
 
 .titlebar-border {
   border-bottom: 1px solid #e5e5e5;
 }
 
 .titlebar-close-button {
+  background-image: -webkit-image-set(
+    url('chrome://theme/IDR_CLOSE_DIALOG') 1x,
+    url('chrome://theme/IDR_CLOSE_DIALOG@2x') 2x);
   -webkit-app-region: no-drag;
   height: 14px;
   margin: 6px;
   position: absolute;
   right: 0;
   width: 14px;
 }
 
+.titlebar-close-button:active {
+  background-image: -webkit-image-set(
+    url('chrome://theme/IDR_CLOSE_DIALOG_P') 1x,
+    url('chrome://theme/IDR_CLOSE_DIALOG_P@2x') 2x);
+}
+
+.titlebar-close-button:hover {
+  background-image: -webkit-image-set(
+    url('chrome://theme/IDR_CLOSE_DIALOG_H') 1x,
+    url('chrome://theme/IDR_CLOSE_DIALOG_H@2x') 2x);
+}
+
 .content {
   height: auto;
   width: 100%;
 }