Add Object::IsNullOrUndefined(Isolate*) helper method

src/full-codegen/s390/full-codegen-s390.cc

Index: src/full-codegen/s390/full-codegen-s390.cc
diff --git a/src/full-codegen/s390/full-codegen-s390.cc b/src/full-codegen/s390/full-codegen-s390.cc
index c850c6ac4d15a4b5e666b7f04e029128a1ed20a3..74c7f849f3f856be2e446719206bff21525eec81 100644
--- a/src/full-codegen/s390/full-codegen-s390.cc
+++ b/src/full-codegen/s390/full-codegen-s390.cc
@@ -502,10 +502,8 @@ void FullCodeGenerator::StackValueContext::Plug(Handle<Object> lit) const {
 void FullCodeGenerator::TestContext::Plug(Handle<Object> lit) const {
   codegen()->PrepareForBailoutBeforeSplit(condition(), true, true_label_,
                                           false_label_);
-  DCHECK(lit->IsNull(isolate()) || lit->IsUndefined(isolate()) ||
-         !lit->IsUndetectable());
-  if (lit->IsUndefined(isolate()) || lit->IsNull(isolate()) ||
-      lit->IsFalse(isolate())) {
+  DCHECK(lit->IsNullOrUndefined(isolate()) || !lit->IsUndetectable());
+  if (lit->IsNullOrUndefined(isolate()) || lit->IsFalse(isolate())) {
     if (false_label_ != fall_through_) __ b(false_label_);
   } else if (lit->IsTrue(isolate()) || lit->IsJSObject()) {
     if (true_label_ != fall_through_) __ b(true_label_);
@@ -2712,7 +2710,6 @@ BackEdgeTable::BackEdgeState BackEdgeTable::GetBackEdgeState(
          isolate->builtins()->OnStackReplacement()->entry());
   return ON_STACK_REPLACEMENT;
 }
-
 }  // namespace internal
 }  // namespace v8
 #endif  // V8_TARGET_ARCH_S390