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..be4f82b75d50accba488ae80ea4e4fd65cf5d240 100644
--- a/chrome/browser/ui/webui/print_preview/print_preview_ui.h
+++ b/chrome/browser/ui/webui/print_preview/print_preview_ui.h
@@ -18,6 +18,7 @@ struct PrintHostMsg_DidGetPreviewPageCount_Params;
 struct PrintHostMsg_RequestPrintPreview_Params;
 
 namespace base {
+class FilePath;
 class RefCountedBytes;
 }
 
@@ -154,6 +155,10 @@ class PrintPreviewUI : public ConstrainedWebDialogUI {
 
   static void SetDelegateForTesting(TestingDelegate* delegate);
 
+  // Allows for tests to set a file path to print a PDF to. This also initiates
+  // the printing without having to click a button on the print preview dialog.
+  void SetSelectedFileForTesting(const base::FilePath& path);
+
  private:
   friend class PrintPreviewHandlerTest;
   FRIEND_TEST_ALL_PREFIXES(PrintPreviewHandlerTest, StickyMarginsCustom);