DevTools: make toolbar button click targets square

Source/devtools/front_end/sources/uiList.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-item {
-    padding: 3px 8px 4px 8px;
+    padding: 2px 8px 3px 8px;
     position: relative;
     min-height: 18px;
     white-space: nowrap;
 }
 
 .list-item:nth-of-type(2n) {
     background-color: #f8f8f8;
 }
 
 .list-item.selected {
-    background-color: rgb(212, 212, 212);
+    background-color: #dadada;
 }
 
 .list-item.selected > .title {
     font-weight: bold;
 }
 
 .list-item:hover {
     background-color: #eee;
 }
 
@@ skipping 23 matching lines @@
 .list-item.label .subtitle {
     font-style: italic;
     font-weight: bold;
     color: #999;
 }
 
 .list-item.dimmed {
     opacity: 0.6;
     font-style: italic;
 }