Add best-effort/allow rollback flags on WorkItem.

chrome/installer/setup/setup_main.cc

 // Copyright (c) 2012 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/installer/setup/setup_main.h"
 
 #include <windows.h>
 #include <msi.h>
 #include <shellapi.h>
 #include <shlobj.h>
@@ skipping 410 matching lines @@
         reg_root,
         version_key,
         KEY_WOW64_32KEY,
         google_update::kRegCriticalVersionField);
     install_list->AddDeleteRegValueWorkItem(reg_root,
                                             version_key,
                                             KEY_WOW64_32KEY,
                                             google_update::kRegRenameCmdField);
   }
   // old_chrome.exe is still in use in most cases, so ignore failures here.
-  // Make sure this is the last item in the list because it cannot be rolled
-  // back.
-  install_list->AddDeleteTreeWorkItem(chrome_old_exe, temp_path.path())->
-      set_ignore_failure(true);
+  install_list->AddDeleteTreeWorkItem(chrome_old_exe, temp_path.path())
+      ->set_best_effort(true);
 
   installer::InstallStatus ret = installer::RENAME_SUCCESSFUL;
   if (!install_list->Do()) {
     LOG(ERROR) << "Renaming of executables failed. Rolling back any changes.";
     install_list->Rollback();
     ret = installer::RENAME_FAILED;
   }
   // temp_path's dtor will take care of deleting or scheduling itself for
   // deletion at reboot when this scope closes.
   VLOG(1) << "Deleting temporary directory " << temp_path.path().value();
@@ skipping 1403 matching lines @@
     // to pass through, since this is only returned on uninstall which is
     // never invoked directly by Google Update.
     return_code = InstallUtil::GetInstallReturnCode(install_status);
   }
 
   installer::EndPersistentHistogramStorage(installer_state.target_path());
   VLOG(1) << "Installation complete, returning: " << return_code;
 
   return return_code;
 }