Fix style error in runtime/memory_region_test.cc.

Change-Id: I0a34675c71e3ecb65566aa425ac30f5a52837cbb
diff --git a/runtime/memory_region_test.cc b/runtime/memory_region_test.cc
index 50575dd..72e03a4 100644
--- a/runtime/memory_region_test.cc
+++ b/runtime/memory_region_test.cc
@@ -54,4 +54,5 @@
     ASSERT_EQ(expected[i], data[i]);
   }
 }
-}
+
+}  // namespace art