Present the printer list from preferences for Chrome OS.

chrome/browser/ui/webui/print_preview/printer_backend_proxy.cc

Index: chrome/browser/ui/webui/print_preview/printer_backend_proxy.cc
diff --git a/chrome/browser/ui/webui/print_preview/printer_backend_proxy.cc b/chrome/browser/ui/webui/print_preview/printer_backend_proxy.cc
new file mode 100644
index 0000000000000000000000000000000000000000..9f42b5cfbb7c737a7958d7c6887b35796c1b8ebf
--- /dev/null
+++ b/chrome/browser/ui/webui/print_preview/printer_backend_proxy.cc
@@ -0,0 +1,39 @@
+// Copyright 2016 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/ui/webui/print_preview/printer_backend_proxy.h"
+
+#include <string>
+
+#include "base/logging.h"
+#include "base/memory/ref_counted.h"
+#include "content/public/browser/browser_thread.h"
+#include "printing/backend/print_backend.h"
+
+namespace printing {
+
+std::string GetDefaultPrinterOnBlockingPoolThread() {
+  DCHECK(content::BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
+
+  scoped_refptr<printing::PrintBackend> print_backend(
+      printing::PrintBackend::CreateInstance(nullptr));

[Lei Zhang, 2016/10/28 21:55:51]

nit: you can omit printing:: in namespace printing.

[skau, 2016/11/02 22:00:03]

Done.

+
+  std::string default_printer = print_backend->GetDefaultPrinterName();
+  VLOG(1) << "Default Printer: " << default_printer;
+  return default_printer;
+}
+
+PrinterList EnumeratePrintersOnBlockingPoolThread(Profile* /* profile */) {
+  DCHECK(content::BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
+  PrinterList printer_list;
+
+  scoped_refptr<printing::PrintBackend> print_backend(
+      printing::PrintBackend::CreateInstance(nullptr));
+
+  print_backend->EnumeratePrinters(&printer_list);
+
+  return printer_list;
+}
+
+}  // namespace printing