Tests: Simplify SequencedWorkerPoolOwner, call Shutdown on destructor.

chrome/browser/ui/app_list/search/history_unittest.cc

 // Copyright 2013 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 "base/basictypes.h"
 #include "base/bind.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
@@ skipping 81 matching lines @@
 
   // testing::Test overrides:
   void SetUp() override {
     worker_pool_owner_.reset(
         new base::SequencedWorkerPoolOwner(1, "AppLauncherTest"));
     ASSERT_TRUE(temp_dir_.CreateUniqueTempDir());
     CreateHistory();
   }
   void TearDown() override {
     Flush();
-    worker_pool_owner_->pool()->Shutdown();
   }
 
   void CreateHistory() {
     const char kStoreDataFileName[] = "app-launcher-test";
     const base::FilePath data_file =
         temp_dir_.path().AppendASCII(kStoreDataFileName);
     scoped_refptr<DictionaryDataStore> dictionary_data_store(
         new DictionaryDataStore(data_file, worker_pool_owner_->pool().get()));
     history_.reset(new History(scoped_refptr<HistoryDataStore>(
         new HistoryDataStore(dictionary_data_store))));
@@ skipping 181 matching lines @@
 
   // The oldest secondary is gone.
   EXPECT_EQ(UNKNOWN_RESULT, GetResultType("1"));
 
   // Touched oldest survived.
   EXPECT_EQ(PERFECT_SECONDARY, GetResultType("0"));
 }
 
 }  // namespace test
 }  // namespace app_list