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

chrome/browser/sync/test/integration/bookmarks_helper.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/browser/sync/test/integration/bookmarks_helper.h"
 
 #include "base/compiler_specific.h"
 #include "base/file_util.h"
 #include "base/path_service.h"
 #include "base/rand_util.h"
@@ skipping 250 matching lines @@
   for (int i = 0; i < sync_datatype_helper::test()->num_clients(); ++i)
     profiles_which_need_to_wait.push_back(
         sync_datatype_helper::test()->GetProfile(i));
 
   for (size_t i = 0; i < profiles_which_need_to_wait.size(); ++i) {
     Profile* profile = profiles_which_need_to_wait[i];
     HistoryService* history_service =
         HistoryServiceFactory::GetForProfileWithoutCreating(profile);
     base::WaitableEvent done(false, false);
     base::CancelableTaskTracker task_tracker;
-    history_service->ScheduleDBTask(new HistoryEmptyTask(&done), &task_tracker);
+    history_service->ScheduleDBTask(
+        scoped_ptr<history::HistoryDBTask>(
+            new HistoryEmptyTask(&done)),
+        &task_tracker);
     done.Wait();
   }
   // Wait such that any notifications broadcast from one of the history threads
   // to the UI thread are processed.
   content::RunAllPendingInMessageLoop();
 }
 
 // Checks if the favicon in |node_a| from |model_a| matches that of |node_b|
 // from |model_b|. Returns true if they match.
 bool FaviconsMatch(BookmarkModel* model_a,
@@ skipping 531 matching lines @@
 
 std::string IndexedSubfolderName(int i) {
   return base::StringPrintf("Subfolder Name %d", i);
 }
 
 std::string IndexedSubsubfolderName(int i) {
   return base::StringPrintf("Subsubfolder Name %d", i);
 }
 
 }  // namespace bookmarks_helper