Always delete old_chrome.exe last in the rename dance since it cannot be rolled back.

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 360 matching lines @@
   // Move chrome.exe to old_chrome.exe, then move new_chrome.exe to chrome.exe.
   install_list->AddMoveTreeWorkItem(chrome_exe.value(),
                                     chrome_old_exe.value(),
                                     temp_path.path().value(),
                                     WorkItem::ALWAYS_MOVE);
   install_list->AddMoveTreeWorkItem(chrome_new_exe.value(),
                                     chrome_exe.value(),
                                     temp_path.path().value(),
                                     WorkItem::ALWAYS_MOVE);
   install_list->AddDeleteTreeWorkItem(chrome_new_exe, temp_path.path());
-  // old_chrome.exe is still in use in most cases, so ignore failures here.
-  install_list->AddDeleteTreeWorkItem(chrome_old_exe, temp_path.path())->
-      set_ignore_failure(true);
 
   // Add work items to delete the "opv", "cpv", and "cmd" values from all
   // products we're operating on (which including the multi-install binaries).
   const Products& products = installer_state->products();
   HKEY reg_root = installer_state->root_key();
   base::string16 version_key;
   for (Products::const_iterator it = products.begin(); it < products.end();
        ++it) {
     version_key = (*it)->distribution()->GetVersionKey();
     install_list->AddDeleteRegValueWorkItem(reg_root,
                                             version_key,
                                             KEY_WOW64_32KEY,
                                             google_update::kRegOldVersionField);
     install_list->AddDeleteRegValueWorkItem(
         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);
+
   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 1388 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;
 }