Added a test that currently is able to print to pdf.

chrome/browser/resources/print_preview/print_preview.js

 // Copyright (c) 2012 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.
 
 // TODO(rltoscano): Move data/* into print_preview.data namespace
 
 var localStrings = new LocalStrings(templateData);
 
 <include src="component.js"/>
 
@@ skipping 1022 matching lines @@
 <include src="search/cloud_destination_list.js"/>
 <include src="search/recent_destination_list.js"/>
 <include src="search/destination_list_item.js"/>
 <include src="search/destination_search.js"/>
 <include src="search/search_box.js"/>
 <include src="search/fedex_tos.js"/>
 
 window.addEventListener('DOMContentLoaded', function() {
   printPreview = new print_preview.PrintPreview();
   printPreview.initialize();
+
+  function temp() {
+    chrome.send('UILoaded');
+  }
+  (function func() {
+    var settings = $('layout-settings');
+    if (settings.offsetWidth > 10) {

[Lei Zhang, 2014/06/13 22:20:11]

So instead of looping and look for this as the signal that the print preview is
reading, what if you changed onInitialSettingsSet_() to do a chrome.send() to
indicate it's ready. Then the C++ test can call a function in the JS file here
to click() the DOM elements. Also add a chrome.send() call to
onPreviewGenerationDone_() to send another message and listen for that on the
C++ side?

+      if (printPreview) {
+        printPreview.destinationStore_.selectDefaultDestination_();
+        var portrait = document.getElementsByClassName(
+            'layout-settings-landscape-radio')[0];
+        if (portrait) {
+          portrait.click();
+        }
+        setTimeout(temp, 6000);
+      }
+    }
+    else {
+      setTimeout(func, 50);
+    }
+  })();
 });