[runtime] Add PropertyConstness bit to PropertyDetails.

src/property.cc

Index: src/property.cc
diff --git a/src/property.cc b/src/property.cc
index 1c2666b00ac436893c81db3da6280fd8b8b8b6be..1ff1dc63a0796ceb91c70635c416e190f44e23c9 100644
--- a/src/property.cc
+++ b/src/property.cc
@@ -25,13 +25,25 @@ std::ostream& operator<<(std::ostream& os,
 Descriptor Descriptor::DataField(Handle<Name> key, int field_index,
                                  PropertyAttributes attributes,
                                  Representation representation) {
-  return DataField(key, field_index, FieldType::Any(key->GetIsolate()),
-                   attributes, representation);
+  return DataField(key, field_index, attributes, kMutable, representation,
+                   FieldType::Any(key->GetIsolate()));
+}
+
+Descriptor Descriptor::DataField(Handle<Name> key, int field_index,
+                                 PropertyAttributes attributes,
+                                 PropertyConstness constness,
+                                 Representation representation,
+                                 Handle<Object> wrapped_field_type) {
+  DCHECK(wrapped_field_type->IsSmi() || wrapped_field_type->IsWeakCell());
+  PropertyDetails details(kData, attributes, kField, constness, representation,
+                          field_index);
+  return Descriptor(key, wrapped_field_type, details);
 }
 
 // Outputs PropertyDetails as a dictionary details.
 void PropertyDetails::PrintAsSlowTo(std::ostream& os) {
   os << "(";
+  if (constness() == kConst) os << "const ";
   os << (kind() == kData ? "data" : "accessor");
   os << ", dictionary_index: " << dictionary_index();
   os << ", attrs: " << attributes() << ")";
@@ -40,6 +52,7 @@ void PropertyDetails::PrintAsSlowTo(std::ostream& os) {
 // Outputs PropertyDetails as a descriptor array details.
 void PropertyDetails::PrintAsFastTo(std::ostream& os, PrintMode mode) {
   os << "(";
+  if (constness() == kConst) os << "const ";
   os << (kind() == kData ? "data" : "accessor");
   if (location() == kField) {
     os << " field";