Present the printer list from preferences for Chrome OS.

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

+// 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 <memory>
+#include <vector>
+
+#include "base/command_line.h"
+#include "base/values.h"
+#include "chrome/browser/chromeos/printing/printer_pref_manager.h"
+#include "chrome/browser/chromeos/printing/printer_pref_manager_factory.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/common/chrome_switches.h"
+#include "chromeos/printing/printer_configuration.h"
+#include "content/public/browser/browser_thread.h"
+#include "printing/backend/print_backend.h"
+
+namespace printing {
+
+namespace {
+
+printing::PrinterBasicInfo ToBasicInfo(const chromeos::Printer& printer) {
+  PrinterBasicInfo basic_info;
+  basic_info.printer_display_name = printer.display_name();
+  basic_info.printer_name = printer.id();
+  basic_info.printer_description = printer.description();
+  return basic_info;
+}
+
+}  // namespace
+
+std::string GetDefaultPrinterOnBlockingPoolThread() {
+  DCHECK(content::BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
+  // TODO(crbug.com/660898): Add default printers to ChromeOS.
+  return "";
+}
+
+PrinterList EnumeratePrintersOnBlockingPoolThread(Profile* profile) {
+  DCHECK(content::BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
+
+  PrinterList printer_list;
+
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableNativeCups)) {
+    chromeos::PrinterPrefManager* prefs =
+        chromeos::PrinterPrefManagerFactory::GetForBrowserContext(profile);
+    std::vector<std::unique_ptr<chromeos::Printer>> printers =
+        prefs->GetPrinters();
+    for (const std::unique_ptr<chromeos::Printer>& printer : printers) {
+      printer_list.push_back(ToBasicInfo(*printer));
+    }
+  }
+
+  return printer_list;
+}
+
+}  // namespace printing