Make HistoryDBTask not refcounted, and ensure it's destroyed on its origin thread.

chrome/test/base/testing_profile.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/test/base/testing_profile.h"
 
 #include "base/base_paths.h"
 #include "base/command_line.h"
 #include "base/file_util.h"
 #include "base/message_loop/message_loop_proxy.h"
@@ skipping 833 matching lines @@
   return pref_proxy_config_tracker_.get();
 }
 
 void TestingProfile::BlockUntilHistoryProcessesPendingRequests() {
   HistoryService* history_service =
       HistoryServiceFactory::GetForProfile(this, Profile::EXPLICIT_ACCESS);
   DCHECK(history_service);
   DCHECK(base::MessageLoop::current());
 
   base::CancelableTaskTracker tracker;
-  history_service->ScheduleDBTask(new QuittingHistoryDBTask(), &tracker);
+  history_service->ScheduleDBTask(
+      scoped_ptr<history::HistoryDBTask>(
+          new QuittingHistoryDBTask()),
+      &tracker);
   base::MessageLoop::current()->Run();
 }
 
 chrome_browser_net::Predictor* TestingProfile::GetNetworkPredictor() {
   return NULL;
 }
 
 DevToolsNetworkController* TestingProfile::GetDevToolsNetworkController() {
   return NULL;
 }
@@ skipping 90 matching lines @@
       path_,
       delegate_,
       extension_policy_,
       pref_service_.Pass(),
       incognito_,
       guest_session_,
       supervised_user_id_,
       policy_service_.Pass(),
       testing_factories_));
 }