[ESnext] Implement Object spread

src/ast/prettyprinter.cc

Index: src/ast/prettyprinter.cc
diff --git a/src/ast/prettyprinter.cc b/src/ast/prettyprinter.cc
index f1c603b331f402aeecd3bdc6cf4b98927422448e..47a4b11e38723ec2cbe4f94e2e04edeefbf3ccc2 100644
--- a/src/ast/prettyprinter.cc
+++ b/src/ast/prettyprinter.cc
@@ -1025,6 +1025,9 @@ void AstPrinter::PrintObjectProperties(
       case ObjectLiteral::Property::SETTER:
         prop_kind = "SETTER";
         break;
+      case ObjectLiteral::Property::SPREAD:
+        prop_kind = "SPREAD";
+        break;
     }
     EmbeddedVector<char, 128> buf;
     SNPrintF(buf, "PROPERTY - %s", prop_kind);