Keep prototype maps in dictionary mode until ICs see them

src/string-stream.cc

Index: src/string-stream.cc
diff --git a/src/string-stream.cc b/src/string-stream.cc
index 18a38be0aab3458ee7cdd6258259ffba19f32798..6e61c372d1119c8eeea7f02f85b8cdc050df650b 100644
--- a/src/string-stream.cc
+++ b/src/string-stream.cc
@@ -536,7 +536,7 @@ void StringStream::PrintPrototype(JSFunction* fun, Object* receiver) {
     }
 
     for (PrototypeIterator iter(isolate, JSObject::cast(receiver),
-                                PrototypeIterator::START_AT_RECEIVER);
+                                kStartAtReceiver);
          !iter.IsAtEnd(); iter.Advance()) {
       if (iter.GetCurrent()->IsJSProxy()) break;
       Object* key = iter.GetCurrent<JSObject>()->SlowReverseLookup(fun);