Drop unused Object::GetMarkerMap method

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index ddd97c6c450f17e7942c0cce781021dfe535c26f..3f9a9ca1f7a4b164d905f17a3f2c5cba8c644ef4 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -978,12 +978,6 @@ Handle<Object> Object::GetPrototype(Isolate* isolate,
 }
 
 
-Map* Object::GetMarkerMap(Isolate* isolate) {
-  if (IsSmi()) return isolate->heap()->heap_number_map();
-  return HeapObject::cast(this)->map();
-}
-
-
 Object* Object::GetHash() {
   // The object is either a number, a name, an odd-ball,
   // a real JS object, or a Harmony proxy.