[dart2js] Default to printLegacyStars for debug printing

Change-Id: I504b6ebc4cc323c229d0aa068a874fe1331ddfbe
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/139562
Reviewed-by: Mayank Patke <fishythefish@google.com>
Commit-Queue: Stephen Adams <sra@google.com>

pkg/compiler/lib/src/elements/types.dart

@@ -130,7 +130,7 @@ abstract class DartType {
   @override
   String toString() => toStructuredText();
 
-  String toStructuredText({bool printLegacyStars = false}) =>
+  String toStructuredText({bool printLegacyStars = true}) =>
       _DartTypeToStringVisitor(printLegacyStars).run(this);
 }