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

chrome/browser/resources/pdf/main.js

 // 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.
 
 'use strict';
 
 /**
  * Global PDFViewer object, accessible for testing.
  * @type Object
  */
@@ skipping 24 matching lines @@
   function initViewer(streamDetails) {
     // PDFViewer will handle any messages after it is created.
     window.removeEventListener('message', handleScriptingMessage, false);
     viewer = new PDFViewer(streamDetails);
     while (pendingMessages.length > 0)
       viewer.handleScriptingMessage(pendingMessages.shift());
   }
 
   function generateStreamDetailsAndInitViewer() {
     var url = window.location.search.substring(1);
+
+    // Hack to enable custom scrollbars for print preview on non-retina mac
+    // displays. Remove after crbug.com/466039 is fixed.
+    if (url.indexOf(IS_MAC_PARAM) === 0) {
+      url = url.substring(IS_MAC_PARAM.length);
+      var link = document.createElement('link');
+      link.rel = 'stylesheet';
+      link.type = 'text/css';
+      link.href = 'scrollbars_mac.css';
+      document.getElementsByTagName('head')[0].appendChild(link);
+    }
+
     var streamDetails = {
       streamUrl: url,
       originalUrl: url,
       responseHeaders: '',
       embedded: window.parent != window,
       tabId: -1
     };
     if (!chrome.tabs) {
       initViewer(streamDetails);
       return;
@@ skipping 21 matching lines @@
 
     // If the viewer is started from the browser plugin, getStreamInfo will
     // return the details of the stream.
     chrome.mimeHandlerPrivate.getStreamInfo(function(streamDetails) {
       initViewer(streamDetails);
     });
   };
 
   main();
 })();