Add a browser test that can communicate with the layout test framework and print pdfs.

chrome/browser/ui/webui/print_preview/print_preview_ui.h

Index: chrome/browser/ui/webui/print_preview/print_preview_ui.h
diff --git a/chrome/browser/ui/webui/print_preview/print_preview_ui.h b/chrome/browser/ui/webui/print_preview/print_preview_ui.h
index 7f32261dad683cb41ea074ec27d46de9b11e7d86..44c56522b4f1fb170e6aab95128a0487e8805805 100644
--- a/chrome/browser/ui/webui/print_preview/print_preview_ui.h
+++ b/chrome/browser/ui/webui/print_preview/print_preview_ui.h
@@ -7,6 +7,7 @@
 
 #include <string>
 
+#include "base/files/file_path.h"

[Lei Zhang, 2014/07/17 00:30:37]

you can forward declare instead.

[ivandavid, 2014/07/17 20:49:20]

Done.

 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
@@ -154,6 +155,11 @@ class PrintPreviewUI : public ConstrainedWebDialogUI {
 
   static void SetDelegateForTesting(TestingDelegate* delegate);
 
+  // Allows for tests to set a file path to print a PDF to. This lso initiates

[Lei Zhang, 2014/07/17 00:30:37]

lso?

[ivandavid, 2014/07/17 20:49:21]

Oops, should be 'also.'

+  // the printing without having to click a button on the print preview dialog.
+  void SetSelectedFileForTesting(
+      const base::FilePath& path, int index, void* params);

[Lei Zhang, 2014/07/17 00:30:37]

|index| and |param| are ultimately unused. Omit them here so the caller doesn't
have to deal with it?

[ivandavid, 2014/07/17 20:49:20]

Done.

+
  private:
   friend class PrintPreviewHandlerTest;
   FRIEND_TEST_ALL_PREFIXES(PrintPreviewHandlerTest, StickyMarginsCustom);