Add best-effort/allow rollback flags on WorkItem.

chrome/installer/setup/setup_main.cc

Index: chrome/installer/setup/setup_main.cc
diff --git a/chrome/installer/setup/setup_main.cc b/chrome/installer/setup/setup_main.cc
index 7a4022c43508bb59eb7bc59eb7b76f5069ccb4cf..3409a623775c238cefa1f8b54ee03d4929eb1457 100644
--- a/chrome/installer/setup/setup_main.cc
+++ b/chrome/installer/setup/setup_main.cc
@@ -427,10 +427,8 @@ installer::InstallStatus RenameChromeExecutables(
                                             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()) {