Update JSONReader to take base::StringPiece instead of std::string

base/json/json_reader.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.
 //
 // A JSON parser.  Converts strings of JSON into a Value object (see
 // base/values.h).
 // http://www.ietf.org/rfc/rfc4627.txt?number=4627
 //
 // Known limitations/deviations from the RFC:
 // - Only knows how to parse ints within the range of a signed 32 bit int and
@@ skipping 15 matching lines @@
 // TODO(tc): Add an option to disable comment stripping
 
 #ifndef BASE_JSON_JSON_READER_H_
 #define BASE_JSON_JSON_READER_H_
 #pragma once
 
 #include <string>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
+#include "base/string_piece.h"
 #include "base/memory/scoped_ptr.h"
 
 namespace base {
 class Value;
 
 namespace internal {
 class JSONParser;
 }
 }
 
@@ skipping 42 matching lines @@
   // Constructs a reader with the default options, JSON_PARSE_RFC.
   JSONReader();
 
   // Constructs a reader with custom options.
   explicit JSONReader(int options);
 
   ~JSONReader();
 
   // Reads and parses |json|, returning a Value. The caller owns the returned
   // instance. If |json| is not a properly formed JSON string, returns NULL.
-  static Value* Read(const std::string& json);
+  static Value* Read(const StringPiece& json);
 
   // Reads and parses |json|, returning a Value owned by the caller. The
   // parser respects the given |options|. If the input is not properly formed,
   // returns NULL.
-  static Value* Read(const std::string& json, int options);
+  static Value* Read(const StringPiece& json, int options);
 
   // Reads and parses |json| like Read(). |error_code_out| and |error_msg_out|
   // are optional. If specified and NULL is returned, they will be populated
   // an error code and a formatted error message (including error location if
   // appropriate). Otherwise, they will be unmodified.
-  static Value* ReadAndReturnError(const std::string& json,
+  static Value* ReadAndReturnError(const StringPiece& json,
                                    int options,  // JSONParserOptions
                                    int* error_code_out,
                                    std::string* error_msg_out);
 
   // Converts a JSON parse error code into a human readable message.
   // Returns an empty string if error_code is JSON_NO_ERROR.
   static std::string ErrorCodeToString(JsonParseError error_code);
 
   // Parses an input string into a Value that is owned by the caller.
   Value* ReadToValue(const std::string& json);
 
   // Returns the error code if the last call to ReadToValue() failed.
   // Returns JSON_NO_ERROR otherwise.
   JsonParseError error_code() const;
 
   // Converts error_code_ to a human-readable string, including line and column
   // numbers if appropriate.
   std::string GetErrorMessage() const;
 
  private:
   scoped_ptr<internal::JSONParser> parser_;
 };
 
 }  // namespace base
 
 #endif  // BASE_JSON_JSON_READER_H_