SearchSuggestionParser: Use a StringPiece instead of modifying a string.

components/omnibox/search_suggestion_parser.h

 // Copyright 2014 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 COMPONENTS_OMNIBOX_SEARCH_SUGGESTION_PARSER_H_
 #define COMPONENTS_OMNIBOX_SEARCH_SUGGESTION_PARSER_H_
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/strings/string16.h"
+#include "base/strings/string_piece.h"
 #include "components/omnibox/autocomplete_match.h"
 #include "components/omnibox/autocomplete_match_type.h"
 #include "components/omnibox/suggestion_answer.h"
 #include "url/gurl.h"
 
 class AutocompleteInput;
 class AutocompleteSchemeClassifier;
 
 namespace base {
 class DictionaryValue;
@@ skipping 256 matching lines @@
    private:
     DISALLOW_COPY_AND_ASSIGN(Results);
   };
 
   // Extracts JSON data fetched by |source| and converts it to UTF-8.
   static std::string ExtractJsonData(const net::URLFetcher* source);
 
   // Parses JSON response received from the provider, stripping XSSI
   // protection if needed. Returns the parsed data if successful, NULL
   // otherwise.
-  static scoped_ptr<base::Value> DeserializeJsonData(std::string json_data);
+  static scoped_ptr<base::Value> DeserializeJsonData(
+      base::StringPiece json_data);
 
   // Parses results from the suggest server and updates the appropriate suggest
   // and navigation result lists in |results|. |is_keyword_result| indicates
   // whether the response was received from the keyword provider.
   // Returns whether the appropriate result list members were updated.
   static bool ParseSuggestResults(
       const base::Value& root_val,
       const AutocompleteInput& input,
       const AutocompleteSchemeClassifier& scheme_classifier,
       int default_result_relevance,
       const std::string& languages,
       bool is_keyword_result,
       Results* results);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SearchSuggestionParser);
 };
 
 #endif  // COMPONENTS_OMNIBOX_SEARCH_SUGGESTION_PARSER_H_