Fix a crash on Chrome OS when selecting a file in chrome://net-export/

chrome/browser/ui/webui/net_export_ui.cc

 // Copyright (c) 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/webui/net_export_ui.h"
 
 #include <memory>
 #include <string>
 #include <vector>
 
@@ skipping 282 matching lines @@
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   file_writer_->GetFilePathToCompletedLog(
       base::Bind(&NetExportMessageHandler::ShowFileInShell, AsWeakPtr()));
 }
 
 void NetExportMessageHandler::FileSelected(const base::FilePath& path,
                                            int index,
                                            void* params) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   DCHECK(select_file_dialog_);
-  select_file_dialog_ = nullptr;
   *last_save_dir.Pointer() = path.DirName();
 
   file_writer_->StartNetLog(path, capture_mode_, GetURLRequestContexts());
+
+  // IMPORTANT: resetting the dialog may lead to the deletion of |path|, so keep
+  // this line last.
+  select_file_dialog_ = nullptr;
 }
 
 void NetExportMessageHandler::FileSelectionCanceled(void* params) {
   DCHECK(select_file_dialog_);
   select_file_dialog_ = nullptr;
 }
 
 void NetExportMessageHandler::OnNewState(const base::DictionaryValue& state) {
   NotifyUIWithState(state.CreateDeepCopy());
 }
@@ skipping 89 matching lines @@
 
 }  // namespace
 
 NetExportUI::NetExportUI(content::WebUI* web_ui) : WebUIController(web_ui) {
   web_ui->AddMessageHandler(base::MakeUnique<NetExportMessageHandler>());
 
   // Set up the chrome://net-export/ source.
   Profile* profile = Profile::FromWebUI(web_ui);
   content::WebUIDataSource::Add(profile, CreateNetExportHTMLSource());
 }