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

printing/backend/print_backend.h

Index: printing/backend/print_backend.h
diff --git a/printing/backend/print_backend.h b/printing/backend/print_backend.h
index 5086d2047346f111cdd7ba5ed8bb94a0c5c2a9a1..2d82b5e461b5796b0d4c67dea1c53a6f48b7fdbf 100644
--- a/printing/backend/print_backend.h
+++ b/printing/backend/print_backend.h
@@ -123,9 +123,14 @@ class PRINTING_EXPORT PrintBackend
   static scoped_refptr<PrintBackend> CreateInstance(
       const base::DictionaryValue* print_backend_settings);
 
+  static void SetNativeCupsEnabled(bool enabled);
+
  protected:
   friend class base::RefCountedThreadSafe<PrintBackend>;
   virtual ~PrintBackend();
+
+ private:
+  static bool native_cups_enabled;

[Lei Zhang, 2016/06/28 22:27:35]

You can just declare this in an anonymous namespace in the .cc file. Since most
Chromium .cc files contain only one class impl, you are not losing out on any
encapsulation. This can also be infinitely complex and you won't have to expose
what it is in the header.

[skau, 2016/06/28 23:58:19]

Done.

 };
 
 }  // namespace printing