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

chrome/browser/ui/webui/print_preview_handler.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_PRINT_PREVIEW_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_PRINT_PREVIEW_HANDLER_H_
 #pragma once
 
 #include "base/ref_counted.h"
 #include "base/weak_ptr.h"
@@ skipping 14 matching lines @@
 
   // WebUIMessageHandler implementation.
   virtual void RegisterMessages();
 
  private:
   friend class EnumeratePrintersTaskProxy;
 
   // Get the list of printers. |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);
 
   // Send the list of printers to the Web UI.
   void SendPrinterList(const ListValue& printers);
 
   // Pointer to current print system.
   scoped_refptr<printing::PrintBackend> print_backend_;
 
   DISALLOW_COPY_AND_ASSIGN(PrintPreviewHandler);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_PRINT_PREVIEW_HANDLER_H_