Prevent unused-variable warnings in the CrOS build with gcc 4.6.

chrome/browser/chromeos/login/existing_user_controller.cc

 // Copyright (c) 2011 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/chromeos/login/existing_user_controller.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/logging.h"
@@ skipping 353 matching lines @@
 
   bool has_cookies =
       login_performer_->auth_mode() == LoginPerformer::AUTH_MODE_EXTENSION;
 
   // LoginPerformer instance will delete itself once online auth result is OK.
   // In case of failure it'll bring up ScreenLock and ask for
   // correct password/display error message.
   // Even in case when following online,offline protocol and returning
   // requests_pending = false, let LoginPerformer delete itself.
   login_performer_->set_delegate(NULL);
-  LoginPerformer* performer = login_performer_.release();
-  performer = NULL;
+  ignore_result(login_performer_.release());
 
   // Will call OnProfilePrepared() in the end.
   LoginUtils::Get()->PrepareProfile(username,
                                     password,
                                     credentials,
                                     pending_requests,
                                     using_oauth,
                                     has_cookies,
                                     this);
 
@@ skipping 201 matching lines @@
     cryptohomed->AsyncSetOwnerUser(
         UserCrosSettingsProvider::cached_owner(), NULL);
 
     // Do not invoke AsyncDoAutomaticFreeDiskSpaceControl(NULL) here
     // so it does not delay the following mount. Cleanup will be
     // started in Cryptohomed by timer.
   }
 }
 
 }  // namespace chromeos