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

printing/backend/print_backend_chromeos.cc

Index: printing/backend/print_backend_chromeos.cc
diff --git a/printing/backend/print_backend_chromeos.cc b/printing/backend/print_backend_chromeos.cc
index f32bbe1e865cd28656aaa9bc65550af4c7f0a173..0553d0ab7d30b8f66c7dae78591274be8feb5ec3 100644
--- a/printing/backend/print_backend_chromeos.cc
+++ b/printing/backend/print_backend_chromeos.cc
@@ -5,6 +5,13 @@
 #include "printing/backend/print_backend.h"
 
 #include "base/logging.h"
+#include "base/values.h"
+#include "printing/backend/print_backend_consts.h"
+#include "url/gurl.h"
+
+#if defined(USE_CUPS)
+#include "printing/backend/print_backend_cups.h"
+#endif  // defined(USE_CUPS)
 
 namespace printing {
 
@@ -72,8 +79,27 @@ bool PrintBackendChromeOS::IsValidPrinter(const std::string& printer_name) {
 
 scoped_refptr<PrintBackend> PrintBackend::CreateInstance(
     const base::DictionaryValue* print_backend_settings) {
+  if (PrintBackend::GetNativeCupsEnabled()) {

[Lei Zhang, 2016/06/29 00:22:31]

Does it work if you omit PrintBackend:: ?

[skau, 2016/06/29 00:40:17]

It does!

+#if defined(USE_CUPS)
+    std::string print_server_url_str;
+    std::string cups_blocking;
+    int encryption = HTTP_ENCRYPT_NEVER;
+    if (print_backend_settings) {
+      print_backend_settings->GetString(kCUPSPrintServerURL,
+                                        &print_server_url_str);
+
+      print_backend_settings->GetString(kCUPSBlocking, &cups_blocking);
+
+      print_backend_settings->GetInteger(kCUPSEncryption, &encryption);
+    }
+    GURL print_server_url(print_server_url_str.c_str());
+    return new PrintBackendCUPS(print_server_url,
+                                static_cast<http_encryption_t>(encryption),
+                                cups_blocking == kValueTrue);
+#endif  // defined(USE_CUPS)
+  }
+
   return new PrintBackendChromeOS();
 }
 
 }  // namespace printing
-