Componentize IDR_NET_ERROR_HTML for sharing it with iOS.

components/neterror/resources/neterror.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. */
 
 /* Don't use the main frame div when the error is in a subframe. */
 html[subframe] #main-frame-error {
   display: none;
 }
 
 /* Don't use the subframe error div when the error is in a main frame. */
@@ skipping 33 matching lines @@
   -webkit-user-select: none;
   display: inline-block;
 }
 
 .icon-generic {
   /**
    * Can't access chrome://theme/IDR_ERROR_NETWORK_GENERIC from an untrusted
    * renderer process, so embed the resource manually.
    */
   content: -webkit-image-set(
-      url(default_100_percent/common/error_network_generic.png) 1x,
-      url(default_200_percent/common/error_network_generic.png) 2x);
+      url(../../resources/default_100_percent/neterror/error_network_generic.png) 1x,
+      url(../../resources/default_200_percent/neterror/error_network_generic.png) 2x);
 }
 
 .icon-offline {
   content: -webkit-image-set(
       url(default_100_percent/offline/100-error-offline.png) 1x,
       url(default_200_percent/offline/200-error-offline.png) 2x);
   position: relative;
 }
 
 .icon-disabled {
@@ skipping 26 matching lines @@
 
 #suggestion {
   margin-top: 15px;
 }
 
 #short-suggestion {
   margin-top: 5px;
 }
 
 #sub-frame-error-details {
+<if expr="is_ios">
+  font-size: 8pt;
+</if>
   color: #8F8F8F;
 <if expr="not is_android and not is_ios">
   /* Not done on mobile for performance reasons. */
   text-shadow: 0 1px 0 rgba(255,255,255,0.3);
 </if>
 }
 
 [jscontent=failedUrl] {
   overflow-wrap: break-word;
 }
@@ skipping 26 matching lines @@
   display: flex;
   height: 30px;
   margin: 0;
   padding: 0;
   width: 60px;
 }
 
 #search-image {
   content:
       -webkit-image-set(
-          url(../../app/theme/default_100_percent/common/omnibox_search_button_loupe.png) 1x,
-          url(../../app/theme/default_200_percent/common/omnibox_search_button_loupe.png) 2x);
+          url(../../resources/default_100_percent/omnibox/omnibox_search_button_loupe.png) 1x,
+          url(../../resources/default_200_percent/omnibox/omnibox_search_button_loupe.png) 2x);
   margin: auto;
 }
 
 .secondary-button {
   -webkit-margin-end: 16px;
   background: #d9d9d9;
   color: #696969;
 }
 
 .snackbar {
@@ skipping 300 matching lines @@
     overflow: inherit;
     padding: 0 8px;
   }
 }
 
 @media (max-width: 120px) {
   button {
     width: auto;
   }
 }