Use custom scrollbars for print preview on non-retina mac displays.

chrome/browser/resources/pdf/pdf.js

 // 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.
 
 'use strict';
 
 /**
  * @return {number} Width of a scrollbar in pixels
  */
 function getScrollbarWidth() {
@@ skipping 57 matching lines @@
   this.streamDetails_ = streamDetails;
   this.loaded_ = false;
   this.parentWindow_ = null;
 
   this.delayedScriptingMessages_ = [];
 
   this.isPrintPreview_ =
       this.streamDetails_.originalUrl.indexOf('chrome://print') == 0;
   this.isMaterial_ = location.pathname.substring(1) === 'index-material.html';
 
+  // Hack to enable custom scrollbars for print preview on non-retina mac
+  // displays. Remove after crbug.com/466039 is fixed.
+  if (this.isPrintPreview_) {
+    var link = document.createElement('link');
+    link.rel = 'stylesheet';
+    link.type = 'text/css';
+    link.href = 'scrollbars-mac.css';
+    document.getElementsByTagName('head')[0].appendChild(link);
+  }
+
   // The sizer element is placed behind the plugin element to cause scrollbars
   // to be displayed in the window. It is sized according to the document size
   // of the pdf and zoom level.
   this.sizer_ = $('sizer');
   this.toolbar_ = $('toolbar');
   this.pageIndicator_ = $('page-indicator');
   this.progressBar_ = $('progress-bar');
   this.passwordScreen_ = $('password-screen');
   this.passwordScreen_.addEventListener('password-submitted',
                                         this.onPasswordSubmitted_.bind(this));
@@ skipping 714 matching lines @@
    * Each bookmark is an Object containing a:
    * - title
    * - page (optional)
    * - array of children (themselves bookmarks)
    * @type {Array} the top-level bookmarks of the PDF.
    */
   get bookmarks() {
     return this.bookmarks_;
   }
 };