Prepopulating "Print To PDF" select file dialog with a suggested filename and path.

chrome/browser/resources/print_preview.js

 // Copyright (c) 2011 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.
 
 var localStrings = new LocalStrings();
 var hasPDFPlugin = true;
 var expectedPageCount = 0;
 var pageRangesInfo = [];
 var printJobTitle = '';
 
@@ skipping 197 matching lines @@
   var printToPDF = (printerName == localStrings.getString('printToPDF'));
 
   return JSON.stringify({'printerName': printerName,
                          'pageRange': pageRangesInfo,
                          'printAll': printAll,
                          'twoSided': twoSided,
                          'copies': copies,
                          'collate': collate,
                          'landscape': landscape,
                          'color': color,
-                         'printToPDF': printToPDF});
+                         'printToPDF': printToPDF,
+                         'printJobTitle': printJobTitle});
 }
 
 /**
  * Asks the browser to print the preview PDF based on current print settings.
  */
 function printFile() {
   chrome.send('print', [getSettingsJSON()]);
 }
 
 /**
@@ skipping 161 matching lines @@
  * Depending on the validity of 'copies' value, enables/disables the print
  * button.
  */
 function updatePrintButtonState() {
   $('print-button').disabled = (!($('all-pages').checked ||
                                   $('pages').checkValidity()) ||
                                 !$('copies').checkValidity());
 }
 
 window.addEventListener('DOMContentLoaded', load);