Enable the cups backend when --enable-native-cups is specified.

printing/backend/print_backend.cc

 // Copyright (c) 2012 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 "printing/backend/print_backend.h"
 
+namespace {
+bool g_native_cups_enabled = false;
+}  // namespace
+
 namespace printing {
 
 PrinterBasicInfo::PrinterBasicInfo()
     : printer_status(0),
       is_default(false) {}
 
 PrinterBasicInfo::PrinterBasicInfo(const PrinterBasicInfo& other) = default;
 
 PrinterBasicInfo::~PrinterBasicInfo() {}
 
@@ skipping 16 matching lines @@
 
 PrinterCapsAndDefaults::PrinterCapsAndDefaults() {}
 
 PrinterCapsAndDefaults::PrinterCapsAndDefaults(
     const PrinterCapsAndDefaults& other) = default;
 
 PrinterCapsAndDefaults::~PrinterCapsAndDefaults() {}
 
 PrintBackend::~PrintBackend() {}
 
+// static
+bool PrintBackend::GetNativeCupsEnabled() {
+  return g_native_cups_enabled;
+}
+
+// static
+void PrintBackend::SetNativeCupsEnabled(bool enabled) {
+  g_native_cups_enabled = enabled;
+}
+
 }  // namespace printing