[scheduling] Use ScopedTaskEnvironment instead of MessageLoop in sync_sessions

MessageLoop will go away, eventually.

BUG=891670

Change-Id: I4e776d210c338961a5225b33a858d3376fb94fb8
Reviewed-on: https://chromium-review.googlesource.com/c/1353920Reviewed-by: Tatiana Gornak <melandory@chromium.org>
Commit-Queue: Carlos Caballero <carlscab@google.com>
Cr-Commit-Position: refs/heads/master@{#613072}

components/sync_sessions/lost_navigations_recorder_unittest.cc

@@ -7,8 +7,8 @@
 #include <memory>
 #include <string>
 
-#include "base/message_loop/message_loop.h"
 #include "base/test/metrics/histogram_tester.h"
+#include "base/test/scoped_task_environment.h"
 #include "components/sync/syncable/entry.h"
 #include "components/sync/syncable/mutable_entry.h"
 #include "components/sync/syncable/syncable_base_transaction.h"
@@ -121,7 +121,7 @@ class LostNavigationsRecorderTest : public testing::Test {
   }
 
  private:
-  base::MessageLoop message_loop;
+  base::test::ScopedTaskEnvironment task_environment_;
   int _id;
   LostNavigationsRecorder recorder_;
   syncer::TestDirectorySetterUpper dir_maker_;

components/sync_sessions/session_store_unittest.cc

@@ -9,9 +9,9 @@
 #include <vector>
 
 #include "base/bind_helpers.h"
-#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/test/mock_callback.h"
+#include "base/test/scoped_task_environment.h"
 #include "components/prefs/testing_pref_service.h"
 #include "components/sync/base/hash_util.h"
 #include "components/sync/device_info/device_info.h"
@@ -180,7 +180,7 @@ class SessionStoreFactoryTest : public ::testing::Test {
 
   ~SessionStoreFactoryTest() override {}
 
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment task_environment_;
   const syncer::DeviceInfo local_device_info_;
   TestingPrefServiceSimple pref_service_;
   SessionSyncPrefs session_sync_prefs_;

components/sync_sessions/session_sync_bridge_unittest.cc

@@ -11,11 +11,11 @@
 #include "base/bind_helpers.h"
 #include "base/json/json_writer.h"
 #include "base/memory/weak_ptr.h"
-#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/strings/stringprintf.h"
 #include "base/test/bind_test_util.h"
 #include "base/test/mock_callback.h"
+#include "base/test/scoped_task_environment.h"
 #include "components/prefs/testing_pref_service.h"
 #include "components/sync/base/hash_util.h"
 #include "components/sync/base/sync_prefs.h"
@@ -324,7 +324,7 @@ class SessionSyncBridgeTest : public ::testing::Test {
   }
 
  private:
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment task_environment_;
   const syncer::DeviceInfo local_device_info_;
   const std::unique_ptr<syncer::ModelTypeStore> store_;