StartPageService: Use a StringPiece instead of modifying a string.

chrome/browser/ui/app_list/start_page_service.cc

 // Copyright 2013 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.
 
 #include "chrome/browser/ui/app_list/start_page_service.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/json/json_string_value_serializer.h"
 #include "base/memory/singleton.h"
 #include "base/metrics/user_metrics.h"
 #include "base/prefs/pref_service.h"
+#include "base/strings/string_piece.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/google/google_profile_helper.h"
 #include "chrome/browser/media/media_stream_infobar_delegate.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/search/hotword_service.h"
 #include "chrome/browser/search/hotword_service_factory.h"
 #include "chrome/browser/ui/app_list/speech_auth_helper.h"
 #include "chrome/browser/ui/app_list/speech_recognizer.h"
 #include "chrome/browser/ui/app_list/start_page_observer.h"
@@ skipping 508 matching lines @@
   doodle_fetcher_->SetLoadFlags(net::LOAD_DO_NOT_SAVE_COOKIES);
   doodle_fetcher_->Start();
 }
 
 void StartPageService::OnURLFetchComplete(const net::URLFetcher* source) {
   std::string json_data;
   source->GetResponseAsString(&json_data);
 
   // Remove XSSI guard for JSON parsing.
   size_t json_start_index = json_data.find("{");
+  base::StringPiece json_data_substr(json_data);
   if (json_start_index != std::string::npos)
-    json_data.erase(0, json_start_index);
+    json_data_substr.remove_prefix(json_start_index);
 
-  JSONStringValueSerializer deserializer(json_data);
+  JSONStringValueSerializer deserializer(json_data_substr);
   deserializer.set_allow_trailing_comma(true);
   int error_code = 0;
   scoped_ptr<base::Value> doodle_json(
       deserializer.Deserialize(&error_code, nullptr));
 
   base::TimeDelta recheck_delay =
       base::TimeDelta::FromMinutes(kDefaultDoodleRecheckDelayMinutes);
 
   if (error_code == 0) {
     base::DictionaryValue* doodle_dictionary = nullptr;
@@ skipping 13 matching lines @@
 
   // Check for a new doodle.
   content::BrowserThread::PostDelayedTask(
       content::BrowserThread::UI, FROM_HERE,
       base::Bind(&StartPageService::FetchDoodleJson,
                  weak_factory_.GetWeakPtr()),
       recheck_delay);
 }
 
 }  // namespace app_list