Cancel the pending print preview request when the user request to show the system dialog.

chrome/browser/ui/webui/print_preview_handler.cc

Index: chrome/browser/ui/webui/print_preview_handler.cc
diff --git a/chrome/browser/ui/webui/print_preview_handler.cc b/chrome/browser/ui/webui/print_preview_handler.cc
index 5d4aae926eb950657778e1080bcff303767e5f3e..fa5544bea12311ba83ba9442f99ece562a686a48 100644
--- a/chrome/browser/ui/webui/print_preview_handler.cc
+++ b/chrome/browser/ui/webui/print_preview_handler.cc
@@ -672,6 +672,10 @@ void PrintPreviewHandler::HandleShowSystemDialog(const ListValue*) {
   printing::PrintViewManager* manager = wrapper->print_view_manager();
   manager->set_observer(this);
   manager->PrintForSystemDialogNow();
+
+  // Cancel the pending preview request if exists.
+  PrintPreviewUI* print_preview_ui = static_cast<PrintPreviewUI*>(web_ui_);
+  print_preview_ui->OnCancelPendingPreviewRequest();
 }
 
 void PrintPreviewHandler::HandleManagePrinters(const ListValue*) {