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

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

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library test.src.serialization.elements_test;
 
 import 'dart:async';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/standard_resolution_map.dart';
@@ skipping 6738 matching lines @@
   void f(int x, int g(String s));
 }
 ''');
     var library = await checkLibrary('''
 import 'a.dart';
 class C extends D {
   void f(int x, g) {}
 }
 ''');
     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';
 class C extends D {
   void f(int x, dynamic g) {}
 }
 ''');
     }
   }
 
@@ skipping 3282 matching lines @@
       fail('Unexpectedly tried to get unlinked summary for $uri');
     }
     return serializedUnit;
   }
 
   @override
   bool hasLibrarySummary(String uri) {
     return true;
   }
 }