Add a new GetInstance() method for singleton classes, take 2.

chrome/test/webdriver/commands/session_with_id.cc

 // Copyright (c) 2010 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/test/webdriver/commands/session_with_id.h"
 
 #include <sstream>
 #include <string>
 
 #include "base/values.h"
@@ skipping 23 matching lines @@
   temp_value->SetString(std::string("platform"), std::string("unknown"));
 #endif
 
   temp_value->SetBoolean(std::string("javascriptEnabled"), true);
 
   response->set_status(kSuccess);
   response->set_value(temp_value);
 }
 
 void SessionWithID::ExecuteDelete(Response* const response) {
-  Singleton<SessionManager>::get()->Delete(session_->id());
+  SessionManager::GetInstance()->Delete(session_->id());
   response->set_status(kSuccess);
 }
 
 }  // namespace webdriver