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

printing/backend/print_backend.h

 // 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.
 
 #ifndef PRINTING_BACKEND_PRINT_BACKEND_H_
 #define PRINTING_BACKEND_PRINT_BACKEND_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 105 matching lines @@
       const std::string& printer_name) = 0;
 
   // Returns true if printer_name points to a valid printer.
   virtual bool IsValidPrinter(const std::string& printer_name) = 0;
 
   // Allocates a print backend. If |print_backend_settings| is nullptr, default
   // settings will be used.
   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
 
 #endif  // PRINTING_BACKEND_PRINT_BACKEND_H_