Print Preview: Hook up the print button to initiate printing without displaying a print dialog.

chrome/browser/ui/webui/print_preview_handler.h

Index: chrome/browser/ui/webui/print_preview_handler.h
diff --git a/chrome/browser/ui/webui/print_preview_handler.h b/chrome/browser/ui/webui/print_preview_handler.h
index 81b1b88dc53447b1909b1f88f94d03ee953387a3..b551d0e0e87fc2eb435d27b4ab48f8940c9492e0 100644
--- a/chrome/browser/ui/webui/print_preview_handler.h
+++ b/chrome/browser/ui/webui/print_preview_handler.h
@@ -28,7 +28,8 @@ class PrintPreviewHandler : public WebUIMessageHandler,
   // Get the list of printers and send it to the Web UI. |args| is unused.
   void HandleGetPrinters(const ListValue* args);
 
-  // Print the preview PDF. |args| is unused.
+  // Get the job settings from Web UI and initiate printing.
+  // First element of |args| is a job settings json string.
   void HandlePrint(const ListValue* args);
 
   // Pointer to current print system.