Introduce IsUndefined(Isolate*) and IsTheHole(Isolate*)

src/heap/heap-inl.h

Index: src/heap/heap-inl.h
diff --git a/src/heap/heap-inl.h b/src/heap/heap-inl.h
index 052eda88be369f89326aa85e5b772095c7b37ff7..29aae24b70247fdc3bb5ed974bcf3abf0904791a 100644
--- a/src/heap/heap-inl.h
+++ b/src/heap/heap-inl.h
@@ -612,12 +612,12 @@ void Heap::ExternalStringTable::Verify() {
   for (int i = 0; i < new_space_strings_.length(); ++i) {
     Object* obj = Object::cast(new_space_strings_[i]);
     DCHECK(heap_->InNewSpace(obj));
-    DCHECK(obj != heap_->the_hole_value());
+    DCHECK(!obj->IsTheHole(heap_->isolate()));
   }
   for (int i = 0; i < old_space_strings_.length(); ++i) {
     Object* obj = Object::cast(old_space_strings_[i]);
     DCHECK(!heap_->InNewSpace(obj));
-    DCHECK(obj != heap_->the_hole_value());
+    DCHECK(!obj->IsTheHole(heap_->isolate()));
   }
 #endif
 }