HiDPI assets for Chrome OS Files app

chrome/browser/resources/file_manager/css/common.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. */
 
 /* This file contains "borrowed" copy of standard styles. To simplify merging,
  * when altering, please preserve original property value by adding comments.
  */
 input.common[type='checkbox'],
 input.common[type='radio'] {
   -webkit-appearance: none;
   -webkit-border-radius: 1px;
   -webkit-box-sizing: border-box;
   border: 1px solid #c6c6c6;
   border-radius: 1px;
   box-sizing: border-box;
   cursor: default;
   height: 13px;
   margin: 0;
   width: 13px;
 }
 
 input.common[type='checkbox'] {
   position: relative;
 }
 
 input.common[type='checkbox']:checked::after {
-  background-image: url('../images/common/check_no_box.png');
+  background-image: -webkit-image-set(
+    url('../images/common/check_no_box.png') 1x,
+    url('../images/common/2x/check_no_box.png') 2x);
   background-position: -3px -4px;
   background-repeat: no-repeat;
 }
 
 input.common[type='checkbox'].white {
   border: none;
 }
 
 input.common[type='checkbox'].white:not(:checked):after {
-  background-image: url('../images/common/checkbox_white_unchecked.png');
+  background-image: -webkit-image-set(
+    url('../images/common/checkbox_white_unchecked.png') 1x,
+    url('../images/common/2x/checkbox_white_unchecked.png') 2x);
   background-position: -1px 0;
 }
 
 input.common[type='checkbox'].white:checked::after {
-  background-image: url('../images/common/checkbox_white_checked.png');
+  background-image: -webkit-image-set(
+    url('../images/common/checkbox_white_checked.png') 1x,
+    url('../images/common/2x/checkbox_white_checked.png') 2x);
   background-position: -1px 0;
 }
 
 input.common[type='checkbox']::after {
   content: '';
   display: -webkit-box;
   height: 15px;
   left: -2px;
   position: absolute;
   top: -2px;
   width: 17px;
 }
 
 .bubble {
   -webkit-border-radius: 2px;
   background: #FFF;
   cursor: default;
   outline: 1px solid rgba(0, 0, 0, 0.2);
   padding: 16px;
 }
 
 .bubble .pointer {
-  background: url('../images/common/bubble_point_white.png');
+  background: -webkit-image-set(
+    url('../images/common/bubble_point_white.png') 1x,
+    url('../images/common/2x/bubble_point_white.png') 2x);
   display: block;
   height: 11px;
   left: 24px;
   margin: 0 0 0 -5px;
   outline: none;
   position: absolute;
   width: 17px;
 }
 
 .bubble .pointer:not(.bottom) {
   top: -11px;
 }
 
 .bubble .pointer.bottom {
   -webkit-transform: rotate(180deg);
   bottom: -11px;
 }
 
 .bubble .close-x {
-  background: url('../images/common/close_x_gray.png');
+  background: -webkit-image-set(
+    url('../images/common/close_x_gray.png') 1x,
+    url('../images/common/2x/close_x_gray.png') 2x);
   height: 21px;
   opacity: 0.3;
   position: absolute;
   right: 3px;
   top: 3px;
   width: 21px;
 }
 
 .bubble .close-x:hover {
   opacity: 0.7;
@@ skipping 84 matching lines @@
 .buttonbar button.menubutton span.disclosureindicator {
   -webkit-transform: rotate(90deg);
   -webkit-transition: none;
   float: right;
   margin-left: 7px;
   margin-top: 10px;
   opacity: .8;
 }
 
 span.disclosureindicator {
-  background: url('../images/disclosure_arrow_dk_grey.png') center no-repeat;
+  background-image: -webkit-image-set(
+    url('../images/common/disclosure_arrow_dk_grey.png') 1x,
+    url('../images/common/2x/disclosure_arrow_dk_grey.png') 2x);
+  background-position: center;
+  background-repeat: no-repeat;
   display: inline-block;
   height: 7px;
   width: 5px;
 }
 
 /* "chrome-menu" class overrides some standard menu.css styles, to make custom
    menus in FileBrowser look like native ChromeOS menus. */
 
 menu.chrome-menu {
   border: 1px solid rgba(0, 0, 0, 0.2);
@@ skipping 23 matching lines @@
   color: rgb(34, 34, 34);
 }
 
 menu.chrome-menu > hr {
   background: rgb(218, 218, 218);
   height: 1px;
   margin: 2px 0;
 }
 
 menu.chrome-menu > :not(hr)[checked] {
-  background-image: url('../images/common/check_no_box.png');
+  background-image: -webkit-image-set(
+    url('../images/common/check_no_box.png') 1x,
+    url('../images/common/2x/check_no_box.png') 2x);
   background-position: 2px center;
 }
 
 menu.chrome-menu > [checked]:before {
   display: none;
 }