Make FileReader return ownership of the string content

extensions/browser/web_ui_user_script_loader.cc

 // 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.
 
 #include "extensions/browser/web_ui_user_script_loader.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/strings/string_util.h"
@@ skipping 109 matching lines @@
           base::Bind(&WebUIUserScriptLoader::OnSingleWebUIURLFetchComplete,
                      base::Unretained(this), &file)));
       fetchers_.push_back(std::move(fetcher));
     }
   }
 }
 
 void WebUIUserScriptLoader::OnSingleWebUIURLFetchComplete(
     extensions::UserScript::File* script_file,
     bool success,
-    const std::string& data) {
+    std::unique_ptr<std::string> data) {
   if (success) {
     // Remove BOM from |data|.
-    if (base::StartsWith(data, base::kUtf8ByteOrderMark,
+    if (base::StartsWith(*data, base::kUtf8ByteOrderMark,
                          base::CompareCase::SENSITIVE)) {
-      script_file->set_content(data.substr(strlen(base::kUtf8ByteOrderMark)));
+      script_file->set_content(data->substr(strlen(base::kUtf8ByteOrderMark)));
     } else {
-      script_file->set_content(data);
+      // TODO(lazyboy): Script files should take ownership of |data|, i.e. the
+      // content of the script.
+      script_file->set_content(*data);
     }
   }
 
   ++complete_fetchers_;
   if (complete_fetchers_ == fetchers_.size()) {
     complete_fetchers_ = 0;
     OnWebUIURLFetchComplete();
     fetchers_.clear();
   }
 }
 
 void WebUIUserScriptLoader::OnWebUIURLFetchComplete() {
   content::BrowserThread::PostTask(
       content::BrowserThread::FILE, FROM_HERE,
       base::Bind(&SerializeOnFileThread, base::Passed(&user_scripts_cache_),
                  scripts_loaded_callback_));
   scripts_loaded_callback_.Reset();
 }