Add support for starting an extension print job to print preview

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

Index: chrome/browser/ui/webui/print_preview/print_preview_handler.h
diff --git a/chrome/browser/ui/webui/print_preview/print_preview_handler.h b/chrome/browser/ui/webui/print_preview/print_preview_handler.h
index f6bf882b55bdd5779e21dcc44f88efa06c877c59..4f0b347fd927e6e86570eb53445ffec6c4098e29 100644
--- a/chrome/browser/ui/webui/print_preview/print_preview_handler.h
+++ b/chrome/browser/ui/webui/print_preview/print_preview_handler.h
@@ -303,6 +303,12 @@ class PrintPreviewHandler
       const std::string& printer_id,
       const base::DictionaryValue& capabilities);
 
+  // Called when an extension print job is completed.
+  // |success|: Whether the job succeeded.
+  // |status|: The returned print job status. Useful for reporting a specific
+  //     error.
+  void OnExtensionPrintResult(bool success, const std::string& status);
+
   // Register/unregister from notifications of changes done to the GAIA
   // cookie.
   void RegisterForMergeSession();