Restore invariant that stack is empty in parseFunctionBody.

pkg/front_end/tool/fasta_perf.dart

Index: pkg/front_end/tool/fasta_perf.dart
diff --git a/pkg/front_end/tool/fasta_perf.dart b/pkg/front_end/tool/fasta_perf.dart
index d8ccbaa4efbdad9b1671acc2ae7cfa71a504cdea..549bdce169ea3ebe4f7d46c99475005dd7ff2d0f 100644
--- a/pkg/front_end/tool/fasta_perf.dart
+++ b/pkg/front_end/tool/fasta_perf.dart
@@ -197,7 +197,7 @@ parseFull(Uri uri, List<int> source) {
 // Note: AstBuilder doesn't build compilation-units or classes, only method
 // bodies. So this listener is not feature complete.
 class _PartialAstBuilder extends AstBuilder {
-  _PartialAstBuilder(Uri uri) : super(null, null, null, null, null, uri);
+  _PartialAstBuilder(Uri uri) : super(null, null, null, null, null, true, uri);
 
   // Note: this method converts the body to kernel, so we skip that here.
   @override