[Extensions] Update Error Console UI

chrome/browser/resources/extensions/extension_error_overlay.css

 /* Copyright 2013 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. */
 
 #extension-error-overlay {
   max-width: 100%;
 }
 
 #extension-error-overlay .content-area {
   display: flex;
   flex-direction: column;
 }
 
+#extension-error-overlay .extension-error-list {
+  border: 1px solid #ccc;
+  margin-bottom: 3px;
+  overflow-y: auto;
+}
+
 .extension-error-overlay-runtime-content {
   flex: none;
 }
 
 #extension-error-overlay .extension-code-highlighted-source {
   background-color: rgba(255, 195, 200, 255);
 }
 
 #extension-error-overlay-code {
   font-size: 1.2em;
@@ skipping 32 matching lines @@
   padding-top: 6px;
 }
 
 .extension-error-overlay-stack-trace-list li:hover {
   background-color: #eee;
 }
 
 .extension-error-overlay-stack-trace-list li.extension-error-active {
   background-color: rgba(0, 100, 255, 0.1);
 }