Add boxing for modified variables

tests/compiler/dart2js_native/dart2js_native.status

Index: tests/compiler/dart2js_native/dart2js_native.status
diff --git a/tests/compiler/dart2js_native/dart2js_native.status b/tests/compiler/dart2js_native/dart2js_native.status
index c5674c1887d327146f2a53c8d09dc1f554d9a2f8..991dd399ca21fd91d9406b4a72ab40fdc3920a45 100644
--- a/tests/compiler/dart2js_native/dart2js_native.status
+++ b/tests/compiler/dart2js_native/dart2js_native.status
@@ -139,7 +139,6 @@ compute_this_script_test: Crash
 core_type_check_native_test: RuntimeError
 event_loop_test: Crash
 fake_thing_test: RuntimeError
-inference_of_helper_methods_test: Crash
 internal_library_test: Crash
 is_check_test: CompileTimeError
 load_elim_refinement_test: CompileTimeError
@@ -147,8 +146,6 @@ mirror_intercepted_field_test: CompileTimeError
 native_class_inheritance1_frog_test: RuntimeError
 native_class_inheritance2_frog_test: RuntimeError
 native_class_inheritance3_frog_test: RuntimeError
-native_exception2_test: Crash
-native_exception_test: Crash
 native_exceptions1_frog_test: Crash
 native_library_same_name_used_frog_test: CompileTimeError
 native_method_inlining_test: Crash
@@ -185,8 +182,6 @@ mirror_intercepted_field_test: CompileTimeError
 native_class_inheritance1_frog_test: RuntimeError
 native_class_inheritance2_frog_test: RuntimeError
 native_class_inheritance3_frog_test: RuntimeError
-native_exception2_test: RuntimeError
-native_exception_test: RuntimeError
 native_exceptions1_frog_test: CompileTimeError
 native_library_same_name_used_frog_test: CompileTimeError
 native_method_inlining_test: Crash # NoSuchMethodError: The method 'accept' was called on null.