Introduce FieldIndex to unify and abstract property/field offset

src/property.cc

Index: src/property.cc
diff --git a/src/property.cc b/src/property.cc
index fa5046de5b1a3c67411a8576b11537a1b4f53653..aad5be8927da0d3f1802f6cd599c68d576bc834d 100644
--- a/src/property.cc
+++ b/src/property.cc
@@ -47,7 +47,13 @@ void LookupResult::Print(FILE* out) {
       break;
     case FIELD:
       PrintF(out, " -type = field\n");
-      PrintF(out, " -index = %d\n", GetFieldIndex().field_index());
+      if (GetFieldIndex().is_inobject()) {
+        PrintF(out, " -index (inobject)= %d\n",
+               GetFieldIndex().property_index());
+      } else {
+        PrintF(out, " -index (out-of-object)= %d\n",
+               GetFieldIndex().property_index());
+      }
       PrintF(out, " -field type:\n");
       GetFieldType()->TypePrint(out);
       break;