PDF: Split elements shared between material and non-material PDF viewers

chrome/browser/resources/pdf/index.css

 /* Copyright 2014 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. */
 
 body {
   background-color: #ccc;
   margin: 0;
 }
 
 viewer-toolbar {
   visibility: hidden;
   white-space: nowrap;
   z-index: 3;
 }
 
 viewer-page-indicator {
   visibility: hidden;
   z-index: 3;
 }
 
 viewer-progress-bar {
   visibility: hidden;
   z-index: 3;
 }
 
-viewer-error-screen {
+viewer-error-screen-legacy {
   visibility: hidden;
   z-index: 2;
 }
 
-viewer-password-screen {
+viewer-password-screen-legacy {
   visibility: hidden;
   z-index: 2;
 }
 
 #plugin {
   height: 100%;
   position: fixed;
   width: 100%;
   z-index: 1;
 }
 
 #sizer {
   position: absolute;
   z-index: 0;
 }