Fix compiling with CUPS 2.2 backend.

printing/backend/cups_helper.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_CUPS_HELPER_H_
 #define PRINTING_BACKEND_CUPS_HELPER_H_
 
 #include <cups/cups.h>
+#include <cups/ppd.h>
 
 #include "base/strings/string_piece.h"
 #include "printing/printing_export.h"
 
 class GURL;
 
 // These are helper functions for dealing with CUPS.
 namespace printing {
 
 struct PrinterSemanticCapsAndDefaults;
@@ skipping 17 matching lines @@
 // Helper function to parse and convert PPD capabilitites to
 // semantic options.
 PRINTING_EXPORT bool ParsePpdCapabilities(
     base::StringPiece printer_name,
     base::StringPiece printer_capabilities,
     PrinterSemanticCapsAndDefaults* printer_info);
 
 }  // namespace printing
 
 #endif  // PRINTING_BACKEND_CUPS_HELPER_H_