Reduce memory consumption of property names.

Property names were always required a string reference which consumed
a large amount of memory for arrays. This patch reduces this consumption
by directly storing the value part of certain strings.

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

jerry-core/ecma/operations/ecma-objects.c

@@ -1259,7 +1259,8 @@ ecma_op_object_get_property_names (ecma_object_t *obj_p, /**< object */
             || ECMA_PROPERTY_GET_TYPE (*property_p) == ECMA_PROPERTY_TYPE_NAMEDACCESSOR)
         {
           ecma_property_pair_t *prop_pair_p = (ecma_property_pair_t *) prop_iter_p;
-          ecma_string_t *name_p = ECMA_GET_NON_NULL_POINTER (ecma_string_t, prop_pair_p->names_cp[i]);
+          ecma_string_t *name_p = ecma_string_from_property_name (*property_p,
+                                                                  prop_pair_p->names_cp[i]);
 
           if (!(is_enumerable_only && !ecma_is_property_enumerable (*property_p)))
           {
@@ -1311,6 +1312,8 @@ ecma_op_object_get_property_names (ecma_object_t *obj_p, /**< object */
               names_hashes_bitmap[bitmap_row] |= (1u << bitmap_column);
             }
           }
+
+          ecma_deref_ecma_string (name_p);
         }
       }