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..330c11e90b118ba4f31b8830c460e4467c11ba4b 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 +694,9 @@ cr.define('print_preview', function() {
     onPreviewGenerationDone_: function() {
       this.isPreviewGenerationInProgress_ = false;
       this.printHeader_.isPrintButtonEnabled = true;
+      if (global['onManipulateSettings']) {

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

This makes it so that the chrome.send() is only used when doing this particular
test.

+        chrome.send('UILoadedForTest');

[Lei Zhang, 2014/06/17 23:22:20]

Although this is just 1 line, consider putting it in a function with a
meaningful name and calling it everywhere, so you avoid typos in the message
name.

[ivandavid, 2014/06/18 00:25:59]

Done. Made a function in native_layer.js since that is where all the
chrome.send() functions seem to be. Its called |doneManipulatingSettings()|.

+      }
       this.printIfReady_();
     },
 
@@ -889,6 +895,72 @@ 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) {

[Lei Zhang, 2014/06/17 23:22:20]

So if your source page is a PDF and not HTML, then I believe there's no layout
control. In that case, this will eval to false and ultimately no UILoadedForTest
message will get sent. That would cause the state machine in the test to not
advance.

+            landscape.click();
+          }
+        } else if (event.layoutSettings == 'PORTRAIT') {
+          //chrome.send('UILoadedForTest');

[Lei Zhang, 2014/06/17 23:22:20]

remove

+          var portrait = document.getElementsByClassName(
+            'layout-settings-portrait-radio')[0];
+          if (portrait) {
+            portrait.click();
+          }
+        }
+      }
+      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('UILoadedForTest');
+        }
+      }
+      else if (event.messageName == 'HEADERS_AND_FOOTERS') {
+        if (event.headersAndFooters == false) {

[Lei Zhang, 2014/06/17 23:22:20]

There's 2x2 matrix of possibilities, where the axis are
|event.headersAndFooters| and |headerFooterCheckbox|'s current value. You should
handle all the cases.

Same for background colors below.

+          var headerFooterCheckbox = document.getElementsByClassName(
+              'header-footer-checkbox');
+          if (headerFooterCheckbox) {
+            this.otherOptionsSettings_.headerFooterCheckbox_.click();
+          }
+        } else {
+          chrome.send('UILoadedForTest');
+        }
+      }
+      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('UILoadedForTest');
+        }
+      }
+      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;

[Lei Zhang, 2014/06/17 23:22:20]

Is this sufficient to cause the PDF to re-render? If so, you probably shouldn't
need to do a chrome.send() on the next line?

[ivandavid, 2014/06/18 00:25:59]

It wasn't. I 'fired' on event which now causes the PDF to re-render.

+           chrome.send('UILoadedForTest');

[Lei Zhang, 2014/06/17 23:22:20]

nit: If you compare this to line 959, one of the two blocks is badly indented.

+        } else {
+          chrome.send('UILoadedForTest');
+        }
+      }
+    },
+
     /**
      * Called when the open-cloud-print-dialog link is clicked. Opens the Google
      * Cloud Print web dialog.