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

chrome/browser/dom_ui/print_preview_handler.cc

 // 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.
 
 #include "chrome/browser/dom_ui/print_preview_handler.h"
 
 #include "base/values.h"
+#include "chrome/browser/dom_ui/web_ui_util.h"
+#include "chrome/browser/renderer_host/render_view_host.h"
 #include "printing/backend/print_backend.h"
 
 PrintPreviewHandler::PrintPreviewHandler()
     : print_backend_(printing::PrintBackend::CreateInstance(NULL)) {
 }
 
 PrintPreviewHandler::~PrintPreviewHandler() {
 }
 
 void PrintPreviewHandler::RegisterMessages() {
   web_ui_->RegisterMessageCallback("getPrinters",
       NewCallback(this, &PrintPreviewHandler::HandleGetPrinters));
+  web_ui_->RegisterMessageCallback("print",
+      NewCallback(this, &PrintPreviewHandler::HandlePrint));
 }
 
 void PrintPreviewHandler::HandleGetPrinters(const ListValue*) {
   ListValue printers;
 
   printing::PrinterList printer_list;
   print_backend_->EnumeratePrinters(&printer_list);
   for (printing::PrinterList::iterator index = printer_list.begin();
        index != printer_list.end(); ++index) {
     printers.Append(new StringValue(index->printer_name));
   }
 
   web_ui_->CallJavascriptFunction(L"setPrinters", printers);
 }
+
+void PrintPreviewHandler::HandlePrint(const ListValue* args) {
+  std::string json_str(
+      web_ui_util::GetJsonResponseFromFirstArgumentInList(args));
+  if (json_str.empty()) {
+    NOTREACHED() << "Empty print job settings";
+    return;
+  }
+  web_ui_->GetRenderViewHost()->PrintForPrintPreview(json_str);
+}