Make FileReader return ownership of the string content

extensions/browser/web_ui_user_script_loader.h

 // Copyright 2015 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 EXTENSIONS_BROWSER_WEB_UI_USER_SCRIPT_LOADER_H_
 #define EXTENSIONS_BROWSER_WEB_UI_USER_SCRIPT_LOADER_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 25 matching lines @@
                   int render_process_id,
                   int render_frame_id) override;
   void LoadScripts(std::unique_ptr<extensions::UserScriptList> user_scripts,
                    const std::set<HostID>& changed_hosts,
                    const std::set<int>& added_script_ids,
                    LoadScriptsCallback callback) override;
 
   // Called at the end of each fetch, tracking whether all fetches are done.
   void OnSingleWebUIURLFetchComplete(extensions::UserScript::File* script_file,
                                      bool success,
-                                     const std::string& data);
+                                     std::unique_ptr<std::string> data);
 
   // Called when the loads of the user scripts are done.
   void OnWebUIURLFetchComplete();
 
   // Creates WebUiURLFetchers for the given |script_files|.
   void CreateWebUIURLFetchers(extensions::UserScript::FileList* script_files,
                               content::BrowserContext* browser_context,
                               int render_process_id,
                               int render_frame_id);
 
@@ skipping 10 matching lines @@
   std::unique_ptr<extensions::UserScriptList> user_scripts_cache_;
 
   LoadScriptsCallback scripts_loaded_callback_;
 
   std::vector<std::unique_ptr<WebUIURLFetcher>> fetchers_;
 
   DISALLOW_COPY_AND_ASSIGN(WebUIUserScriptLoader);
 };
 
 #endif  // EXTENSIONS_BROWSER_WEB_UI_USER_SCRIPT_LOADER_H_