Add ErrorConsole UI for Extension Install Warnings

chrome/browser/resources/extensions/extensions.css

 /* Copyright (c) 2012 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. */
 
 html,
 body {
   height: 100%;
   overflow: hidden;
 }
 
@@ skipping 216 matching lines @@
 .terminated-reload-link {
   -webkit-margin-end: 2.5em;
   padding-top: 7px;
 }
 
 .extension-list-item a {
   -webkit-margin-start: 0.5em;
   display: inline-block;
 }
 
-.install-warnings a {
-  -webkit-margin-start: 0;
-}
-
 .butter-bar,
-.install-warnings,
 .extension-warnings {
   border-radius: 3px;
   margin-top: 5px;
   padding: 2px 5px;
 }
 
 .butter-bar {
   background: rgb(255, 242, 153);
 }
 
-.install-warnings,
 .extension-warnings {
   background: pink;
 }
 
-.install-warnings ul,
 .extension-warnings ul {
   margin: 0;
 }
 
 #font-measuring-div {
   /* Remove from the flow and hide. */
   position: absolute;
   visibility: hidden;
 }
 
@@ skipping 81 matching lines @@
 /* Sideload Wipeout */
 
 .sideload-wipeout-learn-more {
   text-decoration: none;
 }
 
 .sideload-wipeout-banner .page-banner-text {
   -webkit-padding-start: 8px;
   background-image: none;
 }