Switch to using '-t ios' for grit

ui/webui/resources/css/overlay.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. */
 
 /* The shield that overlays the background. */
 .overlay {
   -webkit-box-align: center;
   -webkit-box-orient: vertical;
   -webkit-box-pack: center;
   -webkit-transition: 200ms opacity;
@@ skipping 133 matching lines @@
   display: block;
 }
 
 .overlay .page .button-strip > .default-button:not(:focus) {
   border-color: rgba(0, 0, 0, 0.5);
 }
 
 /* On OSX 10.7, hidden scrollbars may prevent the user from realizing that the
  * overlay contains scrollable content. To resolve this, style the scrollbars on
  * OSX so they are always visible. See http://crbug.com/123010. */
-<if expr="is_macosx">
+<if expr="is_macosx or is_ios">
 .overlay .page .content-area::-webkit-scrollbar {
   -webkit-appearance: none;
   width: 11px;
 }
 
 .overlay .page .content-area::-webkit-scrollbar-thumb {
   background-color: rgba(0, 0, 0, 0.2);
   border: 2px solid white;
   border-radius: 8px;
 }
 
 .overlay .page .content-area::-webkit-scrollbar-thumb:hover {
   background-color: rgba(0, 0, 0, 0.5);
 }
 </if>
 
 .gray-bottom-bar {
   background-color: #f5f5f5;
   border-color: #e7e7e7;
   border-top-style: solid;
   border-width: 1px;
   color: #888;
   display: -webkit-box;
   padding: 14px 17px;
 }