Use ScopedTaskEnvironment instead of MessageLoop in service_manager::test::ServiceTest.

services/preferences/pref_service_factory_unittest.cc

 // Copyright (c) 2017 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 "services/preferences/public/cpp/pref_service_factory.h"
 
 #include "base/files/scoped_temp_dir.h"
 #include "base/memory/ptr_util.h"
-#include "base/message_loop/message_loop.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/test/sequenced_worker_pool_owner.h"
 #include "components/prefs/pref_change_registrar.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
 #include "components/prefs/value_map_pref_store.h"
 #include "components/prefs/writeable_pref_store.h"
 #include "mojo/public/cpp/bindings/binding_set.h"
 #include "services/preferences/public/cpp/dictionary_value_update.h"
 #include "services/preferences/public/cpp/pref_service_main.h"
@@ skipping 52 matching lines @@
       service_factory_bindings_;
   std::unique_ptr<service_manager::ServiceContext> pref_service_context_;
 };
 
 constexpr int kInitialValue = 1;
 constexpr int kUpdatedValue = 2;
 constexpr char kKey[] = "some_key";
 constexpr char kOtherKey[] = "some_other_key";
 constexpr char kDictionaryKey[] = "a.dictionary.pref";
 
-class PrefServiceFactoryTest : public base::MessageLoop::DestructionObserver,
-                               public service_manager::test::ServiceTest {
+class PrefServiceFactoryTest : public service_manager::test::ServiceTest {
  public:
-  PrefServiceFactoryTest() : ServiceTest("prefs_unittests", false) {}
+  PrefServiceFactoryTest()
+      : ServiceTest("prefs_unittests", false),
+        worker_pool_owner_(2, "PrefServiceFactoryTest") {}
 
  protected:
   void SetUp() override {
     ServiceTest::SetUp();
     ASSERT_TRUE(profile_dir_.CreateUniqueTempDir());
 
     // Init the pref service (in production Chrome startup would do this.)
     mojom::PrefServiceControlPtr control;
     connector()->BindInterface(mojom::kServiceName, &control);
     auto config = mojom::PersistentPrefStoreConfiguration::New();
     config->set_simple_configuration(
         mojom::SimplePersistentPrefStoreConfiguration::New(
             profile_dir_.GetPath().AppendASCII("Preferences")));
     control->Init(std::move(config));
     above_user_prefs_pref_store_ = new ValueMapPrefStore();
     below_user_prefs_pref_store_ = new ValueMapPrefStore();
     mojom::PrefStoreRegistryPtr registry;
     connector()->BindInterface(mojom::kServiceName, &registry);
     above_user_prefs_impl_ =
         PrefStoreImpl::Create(registry.get(), above_user_prefs_pref_store_,
                               PrefValueStore::COMMAND_LINE_STORE);
     below_user_prefs_impl_ =
         PrefStoreImpl::Create(registry.get(), below_user_prefs_pref_store_,
                               PrefValueStore::RECOMMENDED_STORE);
   }
 
   // service_manager::test::ServiceTest:
   std::unique_ptr<service_manager::Service> CreateService() override {
-    return base::MakeUnique<ServiceTestClient>(this,
-                                               worker_pool_owner_->pool());
+    return base::MakeUnique<ServiceTestClient>(this, worker_pool_owner_.pool());
   }
 
-  std::unique_ptr<base::MessageLoop> CreateMessageLoop() override {

[fdoray, 2017/05/10 16:53:50]

I doubt that creating the SequencedWorkerPoolOwner right after MessageLoop
matters and is worth the extra complexity.

-    auto loop = ServiceTest::CreateMessageLoop();
-    worker_pool_owner_ = base::MakeUnique<base::SequencedWorkerPoolOwner>(
-        2, "PrefServiceFactoryTest");
-    loop->AddDestructionObserver(this);
-    return loop;
-  }
-
-  // base::MessageLoop::DestructionObserver
-  void WillDestroyCurrentMessageLoop() override { worker_pool_owner_.reset(); }
-
   // Create a fully initialized PrefService synchronously.
   std::unique_ptr<PrefService> Create() {
     std::unique_ptr<PrefService> pref_service;
     base::RunLoop run_loop;
     auto pref_registry = make_scoped_refptr(new PrefRegistrySimple());
     pref_registry->RegisterIntegerPref(kKey, kInitialValue);
     pref_registry->RegisterIntegerPref(kOtherKey, kInitialValue);
     pref_registry->RegisterDictionaryPref(kDictionaryKey);
     ConnectToPrefService(connector(), pref_registry,
                          std::vector<PrefValueStore::PrefStoreType>(),
@@ skipping 41 matching lines @@
   }
 
   static void OnPrefChanged(const base::Closure& quit_closure,
                             const std::string& expected_path,
                             const std::string& path) {
     if (path == expected_path)
       quit_closure.Run();
   }
 
   base::ScopedTempDir profile_dir_;
-  std::unique_ptr<base::SequencedWorkerPoolOwner> worker_pool_owner_;
+  base::SequencedWorkerPoolOwner worker_pool_owner_;
   scoped_refptr<WriteablePrefStore> above_user_prefs_pref_store_;
   std::unique_ptr<PrefStoreImpl> above_user_prefs_impl_;
   scoped_refptr<WriteablePrefStore> below_user_prefs_pref_store_;
   std::unique_ptr<PrefStoreImpl> below_user_prefs_impl_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefServiceFactoryTest);
 };
 
 // Check that a single client can set and read back values.
 TEST_F(PrefServiceFactoryTest, Basic) {
@@ skipping 285 matching lines @@
   }
   PrefChangeRegistrar registrar;
   registrar.Init(pref_service2.get());
   registrar.Add(kDictionaryKey, base::Bind(&Fail, pref_service2.get()));
   pref_service->SetInteger(kKey, kUpdatedValue);
   WaitForPrefChange(pref_service2.get(), kKey);
 }
 
 }  // namespace
 }  // namespace prefs