DevTools: migrate UI.ListWidget icons over to UI.Icon

third_party/WebKit/Source/devtools/front_end/ui/listWidget.css

 /*
  * Copyright 2015 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.
  */
 
 .list {
     flex: auto 0 1;
     overflow-y: auto;
     border: 1px solid rgb(231, 231, 231);
@@ skipping 40 matching lines @@
     align-items: center;
     pointer-events: auto;
 }
 
 .list-item:hover .controls-buttons {
     background-color: hsl(0, 0%, 96%);
 }
 
 .remove-button,
 .edit-button {
-    background-image: url(Images/toolbarButtonGlyphs.png);
-    background-size: 352px 168px;
-    width: 32px;
-    height: 24px;
     opacity: 0.5;
     cursor: pointer;
     flex: none;
     visibility: hidden;
 }
 
-@media (-webkit-min-device-pixel-ratio: 1.1) {
-.remove-button,
-.edit-button {
-    background-image: url(Images/toolbarButtonGlyphs_2x.png);
-}
-} /* media */
-
 .list-item:hover .remove-button,
 .list-item:hover .edit-button {
     visibility: visible;
 }
 
 .remove-button:hover,
 .edit-button:hover {
     opacity: 0.7;
 }
 
@@ skipping 35 matching lines @@
     margin-right: 10px;
 }
 
 .editor-content input {
     margin-right: 10px;
 }
 
 .editor-content input.error-input {
     background-color: white;
 }