Introduce ParameterStructure

pkg/compiler/lib/src/serialization/modelz.dart

Index: pkg/compiler/lib/src/serialization/modelz.dart
diff --git a/pkg/compiler/lib/src/serialization/modelz.dart b/pkg/compiler/lib/src/serialization/modelz.dart
index 6de57cac50617c76618b1255bb72d7659aeae220..41ac5d49d41d85a7d90b9ec74b89bd2df1c80c06 100644
--- a/pkg/compiler/lib/src/serialization/modelz.dart
+++ b/pkg/compiler/lib/src/serialization/modelz.dart
@@ -16,6 +16,7 @@ import '../constants/expressions.dart';
 import '../elements/resolution_types.dart';
 import '../elements/common.dart';
 import '../elements/elements.dart';
+import '../elements/entities.dart';
 import '../elements/modelx.dart' show FunctionSignatureX;
 import '../elements/visitor.dart';
 import '../io/source_file.dart';
@@ -850,6 +851,9 @@ abstract class ParametersMixin
     }
     return _parameters;
   }
+
+  ParameterStructure get parameterStructure =>
+      functionSignature.parameterStructure;
 }
 
 abstract class FunctionTypedElementMixin
@@ -1473,6 +1477,11 @@ class ForwardingConstructorElementZ extends ElementZ
   }
 
   @override
+  ParameterStructure get parameterStructure {
+    return functionSignature.parameterStructure;
+  }
+
+  @override
   bool get hasFunctionSignature {
     return _unsupported('hasFunctionSignature');
   }