DevTools: [MQI] text-shadow for label instead of black background color

Source/devtools/front_end/responsiveDesignView.css

 /*
  * Copyright 2014 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.
  */
 
 .responsive-design {
     overflow: hidden;
     position: relative;
 }
@@ skipping 462 matching lines @@
 .media-inspector-min-label::after {
     position: absolute;
     padding-left: 2px;
     right: -1px;
     height: 6px;
     content: url(Images/graphLabelCalloutLeft.png);
     -webkit-filter: invert(0.8);
 }
 
 .media-inspector-max-label {
-    background-color: rgba(0, 0, 0, 0.5);
+    text-shadow: 0px 0px 2px black;
     padding-left: 11px;
 }
 
-.media-inspector-marker-container:hover .media-inspector-max-label {
-    background-color: rgba(0, 0, 0, 0.3);
-}
-
 .media-inspector-max-label::before {
     position: absolute;
     padding-right: 2px;
     left: -1px;
     height: 6px;
     content: url(Images/graphLabelCalloutRight.png);
     -webkit-filter: invert(0.8);
 }
 
 .media-inspector-threshold-serif {
@@ skipping 30 matching lines @@
 
 @-webkit-keyframes media-inspector-animation-highlight-1 {
     from { -webkit-filter: brightness(135%); }
     to { -webkit-filter: brightness(100%); }
 }
 
 @-webkit-keyframes media-inspector-animation-highlight-2 {
     from { -webkit-filter: brightness(135%); }
     to { -webkit-filter: brightness(100%); }
 }