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

chrome/browser/resources/print_preview/print_preview.js

Index: chrome/browser/resources/print_preview/print_preview.js
diff --git a/chrome/browser/resources/print_preview/print_preview.js b/chrome/browser/resources/print_preview/print_preview.js
index ac3a0ab789135db2746d6fe3b522398b759867d9..87e9fca92e73b66f9d0263e0af560bd7eb2bc13d 100644
--- a/chrome/browser/resources/print_preview/print_preview.js
+++ b/chrome/browser/resources/print_preview/print_preview.js
@@ -285,7 +285,10 @@ cr.define('print_preview', function() {
           this.nativeLayer_,
           print_preview.NativeLayer.EventType.PRIVET_PRINT_FAILED,
           this.onPrivetPrintFailed_.bind(this));
-
+      this.tracker.add(
+          this.nativeLayer_,
+          print_preview.NativeLayer.EventType.MANIPULATE_SETTINGS,
+          this.onManipulateSettings_.bind(this));
 
       this.tracker.add(
           $('system-dialog-link'),
@@ -691,6 +694,7 @@ cr.define('print_preview', function() {
     onPreviewGenerationDone_: function() {
       this.isPreviewGenerationInProgress_ = false;
       this.printHeader_.isPrintButtonEnabled = true;
+      chrome.send('UILoaded');

[Lei Zhang, 2014/06/17 21:57:33]

You may want to rename "UiLoaded" to "UiLoadedForTest". Since it's not normally
needed.

[ivandavid, 2014/06/17 22:59:16]

Done.

       this.printIfReady_();
     },
 
@@ -889,6 +893,67 @@ cr.define('print_preview', function() {
         localStrings.getString('couldNotPrint'));
     },
 
+    onManipulateSettings_: function(event) {
+      if (event.messageName == 'SAVE_AS_PDF') {
+        this.destinationStore_.selectDefaultDestination_();
+      }
+      else if (event.messageName == 'LAYOUT_SETTINGS') {
+        if (event.layoutSettings == 'LANDSCAPE') {
+          var landscape = document.getElementsByClassName(
+            'layout-settings-landscape-radio')[0];
+          if (landscape) {
+            landscape.click();
+          }
+        } else {
+          chrome.send('UILoaded');

[Lei Zhang, 2014/06/17 21:57:33]

Why not click the portrait button in this case? That is, go with the regular
workflow and naturally send a UILoaded event, rather than having to remember to
do it here again.

[ivandavid, 2014/06/17 22:59:16]

I didn't think it would work because its already selected by default. However, I
implemented your change and it worked.

+        }
+      }
+      else if (event.messageName == 'PAGE_NUMBERS') {
+        if (event.pageNumbers != '') {
+          var pageSettingsCustomInput = document.getElementsByClassName(
+              'page-settings-custom-input')[0];
+          if (pageSettingsCustomInput) {
+            pageSettingsCustomInput.value = event.pageSettings;
+          }
+        } else {
+          chrome.send('UILoaded');
+        }
+      }
+      else if (event.messageName == 'HEADERS_AND_FOOTERS') {
+        if (event.headersAndFooters == false) {
+          var headerFooterCheckbox = document.getElementsByClassName(
+              'header-footer-checkbox');
+          if (headerFooterCheckbox) {
+            this.otherOptionsSettings_.headerFooterCheckbox_.click();
+          }
+        } else {
+          chrome.send('UILoaded');
+        }
+      }
+      else if (event.messageName == 'BACKGROUND_COLORS_AND_IMAGES') {
+        if (event.backgroundColorsAndImages == true) {
+          var backgroundCheckbox = document.getElementsByClassName(
+              'css-background-checkbox')[0];
+          if (backgroundCheckbox) {
+            this.otherOptionsSettings_.cssBackgroundCheckbox_.click();
+          }
+        } else {
+          chrome.send('UILoaded');
+        }
+      }
+      else if (event.messageName == 'MARGINS') {
+        var marginSettingsSelect =
+            document.getElementsByClassName('margin-settings-select')[0];
+        var index = parseInt(event.margins, 10);
+        if (marginSettingsSelect && index != 0) {
+           marginSettingsSelect.selectedIndex = index;
+           chrome.send('UILoaded');
+        } else {
+          chrome.send('UILoaded');
+        }
+      }
+    },
+
     /**
      * Called when the open-cloud-print-dialog link is clicked. Opens the Google
      * Cloud Print web dialog.