Present the printer list from preferences for Chrome OS.

chrome/browser/ui/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/chromecast_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//build/split_static_library.gni")
 import("//chrome/common/features.gni")
@@ skipping 2066 matching lines @@
     deps += [ "//chrome/browser:theme_properties" ]
   }
   if (enable_print_preview) {
     sources += [
       "webui/print_preview/extension_printer_handler.cc",
       "webui/print_preview/extension_printer_handler.h",
       "webui/print_preview/print_preview_handler.cc",
       "webui/print_preview/print_preview_handler.h",
       "webui/print_preview/print_preview_ui.cc",
       "webui/print_preview/print_preview_ui.h",
+      "webui/print_preview/printer_backend_proxy.h",
       "webui/print_preview/printer_handler.cc",
       "webui/print_preview/printer_handler.h",
       "webui/print_preview/sticky_settings.cc",
       "webui/print_preview/sticky_settings.h",
     ]
+
+    if (is_chromeos) {
+      sources += [ "webui/print_preview/printer_backend_proxy_chromeos.cc" ]
+    } else {
+      sources += [ "webui/print_preview/printer_backend_proxy.cc" ]
+    }
   }
 
   if (is_android) {
     deps += [
       "//components/navigation_interception",
       "//crypto:platform",
       "//device/usb/mojo",
       "//device/usb/public/interfaces",
       "//ui/android",
     ]
@@ skipping 1325 matching lines @@
       "test/test_confirm_bubble_model.cc",
       "test/test_confirm_bubble_model.h",
     ]
     deps += [ "//chrome/test:test_support_ui" ]
   }
 
   if (enable_extensions) {
     deps += [ "//extensions/browser" ]
   }
 }