Add optional FunctionType.positionalParameterNames and use them to resynthesize function-type forma…

pkg/analyzer/test/src/summary/resynthesize_common.dart

Index: pkg/analyzer/test/src/summary/resynthesize_common.dart
diff --git a/pkg/analyzer/test/src/summary/resynthesize_common.dart b/pkg/analyzer/test/src/summary/resynthesize_common.dart
index 022921658d6a1a4564873162f86933f35e8c9a15..fcf847e07b0e55c75d78c935caef94513de6997c 100644
--- a/pkg/analyzer/test/src/summary/resynthesize_common.dart
+++ b/pkg/analyzer/test/src/summary/resynthesize_common.dart
@@ -6756,12 +6756,24 @@ class C extends D {
 }
 ''');
     if (isStrongMode) {
-      checkElementText(library, r'''
+      if (isSharedFrontEnd) {
+        // Front-end copies FunctionType instances, which means that if it has
+        // parameter names in superclass, then we have names also in the
+        // subclass.
+        checkElementText(library, r'''
+import 'a.dart';
+class C extends D {
+  void f(int x, int g(String s)) {}
+}
+''');
+      } else {
+        checkElementText(library, r'''
 import 'a.dart';
 class C extends D {
   void f(int x, (String) → int g) {}
 }
 ''');
+      }
     } else {
       checkElementText(library, r'''
 import 'a.dart';