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

base/json/json_parser.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 BASE_JSON_JSON_PARSER_H_
 #define BASE_JSON_JSON_PARSER_H_
 #pragma once
 
 #include <string>
 
@@ skipping 48 matching lines @@
 // of a token, such that the next iteration of the parser will be at the byte
 // immediately following the token, which would likely be the first byte of the
 // next token.
 class BASE_EXPORT_PRIVATE JSONParser {
  public:
   explicit JSONParser(int options);
   ~JSONParser();
 
   // Parses the input string according to the set options and returns the
   // result as a Value owned by the caller.
-  Value* Parse(const std::string& input);
+  Value* Parse(const StringPiece& input);
 
   // Returns the error code.
   JSONReader::JsonParseError error_code() const;
 
   // Returns the human-friendly error message.
   std::string GetErrorMessage() const;
 
  private:
   enum Token {
     T_OBJECT_BEGIN,           // {
@@ skipping 184 matching lines @@
   FRIEND_TEST_ALL_PREFIXES(JSONParserTest, ConsumeNumbers);
   FRIEND_TEST_ALL_PREFIXES(JSONParserTest, ErrorMessages);
 
   DISALLOW_COPY_AND_ASSIGN(JSONParser);
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_JSON_JSON_PARSER_H_