Use ScopedTaskEnvironment instead of MessageLoop in storage unit tests.

storage/browser/database/database_quota_client_unittest.cc

Index: storage/browser/database/database_quota_client_unittest.cc
diff --git a/storage/browser/database/database_quota_client_unittest.cc b/storage/browser/database/database_quota_client_unittest.cc
index 7aa592727da7cc7c0babe494f6c406d3ef09b329..db914fc69e2b65cc9f981e5a1ac0b8367698ebbd 100644
--- a/storage/browser/database/database_quota_client_unittest.cc
+++ b/storage/browser/database/database_quota_client_unittest.cc
@@ -12,6 +12,7 @@
 #include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "net/base/completion_callback.h"
 #include "net/base/net_errors.h"
@@ -192,7 +193,7 @@ class DatabaseQuotaClientTest : public testing::Test {
     delete_status_ = status;
   }
 
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   int64_t usage_;
   std::set<GURL> origins_;
   storage::QuotaStatusCode delete_status_;