[DevTools] Hide clear button for empty fields

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

 /*
  * Copyright (c) 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.
  */
 
 :host {
     flex: none;
     padding: 0 2px;
 }
@@ skipping 212 matching lines @@
     opacity: 0.7;
     flex-basis: 13px;
     flex-shrink: 0;
     height: 13px;
 }
 
 .toolbar-input-clear-button:hover {
     opacity: 1;
 }
 
+.toolbar-input-empty .toolbar-input-clear-button {
+    display: none;
+}
+
 /* Separator */
 
 .toolbar-divider {
     background-color: #ccc;
     width: 1px;
     margin: 5px 4px;
     height: 16px;
 }
 
 .toolbar-spacer {
@@ skipping 21 matching lines @@
     margin-top: -1px;
     width: 28px;
     left: -2px;
 }
 
 span.toolbar-select-container.toolbar-item.warning {
     background: #ffd7d7;
     padding: 0 5px 0 0;
     margin-right: 1px;
 }