Material PDF: Support RTL languages

chrome/browser/resources/pdf/elements/viewer-pdf-toolbar/viewer-pdf-toolbar.css

 /* Copyright 2015 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. */
 
 /* We introduce a wrapper aligner element as setting the relevant attributes
  * (horizontal justified layout center) have no effect on the core-toolbar. */
 #aligner {
   width: 100%;
 }
 
 #title {
   font-size: 77.8%;
   font-weight: 500;
   overflow: hidden;
   text-overflow: ellipsis;
   white-space: nowrap;
 }
 
 #pageselector-container {
   text-align: center;
   /* The container resizes according to the width of the toolbar. On small
    * screens with large numbers of pages, overflow page numbers without
    * wrapping. */
   white-space: nowrap;
 }
 
 #buttons {
   -webkit-user-select: none;
-  text-align: right;
+  text-align: end;
 }
 
 paper-icon-button {
-  margin-right: 12px;
+  -webkit-margin-end: 12px;
 }
 
 viewer-toolbar-dropdown {
-  margin-right: 4px;
+  -webkit-margin-end: 4px;
 }
 
 paper-progress {
   --paper-progress-active-color: rgb(50, 54, 57);
   --paper-progress-container-color: rgb(34, 36, 38);
   --paper-progress-height: 48px;
   position: absolute;
   width: 100%;
 }
 
@@ skipping 10 matching lines @@
   background: rgba(255, 255, 255, 0.3);
 }
 
 paper-toolbar /deep/ .toolbar-tools {
   height: 48px;
 }
 
 .invisible {
   visibility: hidden;
 }