Make sure the bubbles are positioned relative to the content-area

chrome/browser/resources/shared/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 91 matching lines @@
    * necessary. See http://crbug.com/119029. */
   margin: 0;
   padding: 14px 17px 14px;
   text-shadow: white 0 1px 2px;
 }
 
 .overlay .page .content-area {
   -webkit-box-flex: 1;
   overflow: auto;
   padding: 6px 17px 6px;
+  position: relative;
 }
 
 .overlay .page .action-area {
   -webkit-box-align: center;
   -webkit-box-orient: horizontal;
   -webkit-box-pack: end;
   display: -webkit-box;
   padding: 14px 17px;
 }
 
@@ skipping 27 matching lines @@
 .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>