[DevTools] Make empty matched styles section zero-height.

third_party/WebKit/Source/devtools/front_end/elements/elementsPanel.css

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc.  All rights reserved.
  * Copyright (C) 2009 Anthony Ricaud <rik@webkit.org>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 137 matching lines @@
 }
 
 .metrics .bottom {
     display: inline-block;
 }
 
 .styles-section {
     padding: 2px 2px 4px 4px;
     min-height: 18px;
     white-space: nowrap;
-    background-origin: padding;
-    background-clip: padding;
     -webkit-user-select: text;
     border-bottom: 1px solid #eee;
     position: relative;
     overflow: hidden;
 }
 
 .styles-section:last-child {
     border-bottom: none;
 }
 
@@ skipping 77 matching lines @@
 .styles-section a[data-uncopyable]::before {
     content: attr(data-uncopyable);
     text-decoration: underline;
 }
 
 .styles-section .style-properties {
     margin: 0;
     padding: 2px 4px 0 0;
     list-style: none;
     clear: both;
+    display: flex;
 }
 
 .styles-section.matched-styles .style-properties {
     padding-left: 0;
 }
 
 .styles-element-state-pane {
     overflow: hidden;
     height: 66px;
     padding-left: 2px;
@@ skipping 260 matching lines @@
     position: absolute;
     right: 0;
     bottom: 0;
     visibility: hidden;
     background-color: rgba(255, 255, 255, 0.9);
 }
 
 .styles-pane:not(.is-editing-style) .styles-section.matched-styles:not(.read-only):hover .sidebar-pane-section-toolbar {
     visibility: visible;
 }