Use ScopedTaskEnvironment instead of MessageLoop in storage unit tests.

storage/browser/fileapi/quota/quota_reservation_manager_unittest.cc

Index: storage/browser/fileapi/quota/quota_reservation_manager_unittest.cc
diff --git a/storage/browser/fileapi/quota/quota_reservation_manager_unittest.cc b/storage/browser/fileapi/quota/quota_reservation_manager_unittest.cc
index a6c344ef73bad8b004eb4d5e471a503decc63beb..22158d0342e9edd499b49ec34bc3bd1152c4d3bb 100644
--- a/storage/browser/fileapi/quota/quota_reservation_manager_unittest.cc
+++ b/storage/browser/fileapi/quota/quota_reservation_manager_unittest.cc
@@ -16,6 +16,7 @@
 #include "base/macros.h"
 #include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "storage/browser/fileapi/quota/open_file_handle.h"
 #include "storage/browser/fileapi/quota/quota_reservation.h"
@@ -208,7 +209,7 @@ class QuotaReservationManagerTest : public testing::Test {
   const base::FilePath& file_path() const { return file_path_; }
 
  private:
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   base::ScopedTempDir work_dir_;
   base::FilePath file_path_;
   std::unique_ptr<QuotaReservationManager> reservation_manager_;