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..3fe31418bef7eea355eed6b4e975d5091d0ff6e3 100644
--- a/printing/backend/print_backend_chromeos.cc
+++ b/printing/backend/print_backend_chromeos.cc
@@ -4,7 +4,14 @@
 
 #include "printing/backend/print_backend.h"
 
+#include "base/command_line.h"
 #include "base/logging.h"
+#include "base/values.h"
+#include "chrome/common/chrome_switches.h"
+#include "printing/backend/cups_helper.h"
+#include "printing/backend/print_backend_consts.h"
+#include "printing/backend/print_backend_cups.h"
+#include "url/gurl.h"
 
 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 (base::CommandLine::ForCurrentProcess()->HasSwitch(

[Lei Zhang, 2016/06/28 19:09:47]

Given that PrintBackend::CreateInstance() has many implementations, changing its
signature is a pain. Assuming |kEnableNativeCups| is not going to be around
forever, maybe just add a static method to set a global boolean in this file.

Set the global from chrome/ to break the dependency.

[skau, 2016/06/28 21:40:15]

Done.

+          switches::kEnableNativeCups)) {
+#ifdef USE_CUPS

[Lei Zhang, 2016/06/28 19:09:47]

nit: #if defined(USE_CUPS)

[skau, 2016/06/28 21:40:15]

Done.

+    std::string print_server_url_str, cups_blocking;

[Lei Zhang, 2016/06/28 19:09:47]

nit: one decl per line

[skau, 2016/06/28 21:40:15]

Done.

+    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  // USE_CUPS
+  }
+
   return new PrintBackendChromeOS();
 }
 
 }  // namespace printing
-