Add Object::IsNullOrUndefined(Isolate*) helper method

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 3eda230a939a1b5163516c1bdec461972e117a34..53c5e18c53dc60602d28997bffa3236ec2b04ffb 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1162,11 +1162,14 @@ class Object {
   OBJECT_TYPE_LIST(IS_TYPE_FUNCTION_DECL)
   HEAP_OBJECT_TYPE_LIST(IS_TYPE_FUNCTION_DECL)
 #undef IS_TYPE_FUNCTION_DECL
+
 #define IS_TYPE_FUNCTION_DECL(Type, Value) \
   INLINE(bool Is##Type(Isolate* isolate) const);
   ODDBALL_LIST(IS_TYPE_FUNCTION_DECL)
 #undef IS_TYPE_FUNCTION_DECL
 
+  INLINE(bool IsNullOrUndefined(Isolate* isolate) const);
+
   // A non-keyed store is of the form a.x = foo or a["x"] = foo whereas
   // a keyed store is of the form a[expression] = foo.
   enum StoreFromKeyed {
@@ -1711,6 +1714,8 @@ class HeapObject: public Object {
   ODDBALL_LIST(IS_TYPE_FUNCTION_DECL)
 #undef IS_TYPE_FUNCTION_DECL
 
+  INLINE(bool IsNullOrUndefined(Isolate* isolate) const);
+
 #define DECLARE_STRUCT_PREDICATE(NAME, Name, name) \
   INLINE(bool Is##Name() const);
   STRUCT_LIST(DECLARE_STRUCT_PREDICATE)