Use StringPiece in cups_helper.cc.

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 <string>
-
+#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;
 
 // Helper wrapper around http_t structure, with connection and cleanup
 // functionality.
 class PRINTING_EXPORT HttpConnectionCUPS {
  public:
   HttpConnectionCUPS(const GURL& print_server_url,
                      http_encryption_t encryption);
   ~HttpConnectionCUPS();
 
   void SetBlocking(bool blocking);
 
   http_t* http();
 
  private:
   http_t* http_;
 };
 
 // Helper function to parse and convert PPD capabilitites to
 // semantic options.
 PRINTING_EXPORT bool ParsePpdCapabilities(
-    const std::string& printer_name,
-    const std::string& printer_capabilities,
+    base::StringPiece printer_name,
+    base::StringPiece printer_capabilities,
     PrinterSemanticCapsAndDefaults* printer_info);
 
 }  // namespace printing
 
 #endif  // PRINTING_BACKEND_CUPS_HELPER_H_