Present the printer list from preferences for Chrome OS.

chrome/browser/ui/BUILD.gn

Index: chrome/browser/ui/BUILD.gn
diff --git a/chrome/browser/ui/BUILD.gn b/chrome/browser/ui/BUILD.gn
index a0c509d8bb55777047e8e3de59ee78cc1ed9d0ba..4cbdb6575a8afb08aeb6780adcaceb6267c7db94 100644
--- a/chrome/browser/ui/BUILD.gn
+++ b/chrome/browser/ui/BUILD.gn
@@ -2084,11 +2084,18 @@ split_static_library("ui") {
       "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) {