[scheduling] Use ScopedTaskEnvironment instead of MessageLoop in consent_auditor

MessageLoop will go away, eventually.

BUG=891670

Change-Id: Iaf5b03e03f678986e2ac179eff58b780858cf21c
Reviewed-on: https://chromium-review.googlesource.com/c/1352776Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Carlos Caballero <carlscab@google.com>
Cr-Commit-Position: refs/heads/master@{#612127}

components/consent_auditor/consent_sync_bridge_impl_unittest.cc

@@ -10,8 +10,8 @@
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
-#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "components/sync/model/data_batch.h"
 #include "components/sync/model/mock_model_type_change_processor.h"
 #include "components/sync/model/model_type_store_test_util.h"
@@ -154,7 +154,7 @@ class ConsentSyncBridgeImplTest : public testing::Test {
   }
 
  private:
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment task_environment_;
   testing::NiceMock<MockModelTypeChangeProcessor> mock_processor_;
   std::unique_ptr<ConsentSyncBridgeImpl> bridge_;
 };