Add Object::IsNullOrUndefined(Isolate*) helper method

src/full-codegen/ppc/full-codegen-ppc.cc

Index: src/full-codegen/ppc/full-codegen-ppc.cc
diff --git a/src/full-codegen/ppc/full-codegen-ppc.cc b/src/full-codegen/ppc/full-codegen-ppc.cc
index 7598d2872f62314b5dd722b890780f15ecd7fb16..c2b0139eb81dd4b83e55bf44b2167ca701e8b1f3 100644
--- a/src/full-codegen/ppc/full-codegen-ppc.cc
+++ b/src/full-codegen/ppc/full-codegen-ppc.cc
@@ -511,10 +511,8 @@ 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_);