Resynthesize constructor initializers from Kernel.

pkg/front_end/lib/src/fasta/kernel/kernel_target.dart

 // Copyright (c) 2016, 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 fasta.kernel_target;
 
 import 'dart:async' show Future;
 
 import 'package:kernel/ast.dart'
     show
@@ skipping 544 matching lines @@
           superTarget ??= defaultSuperConstructor(cls);
           Initializer initializer;
           if (superTarget == null) {
             builder.addCompileTimeError(
                 templateSuperclassHasNoDefaultConstructor
                     .withArguments(cls.superclass.name),
                 constructor.fileOffset);
             initializer = new InvalidInitializer();
           } else {
             initializer =
-                new SuperInitializer(superTarget, new Arguments.empty());
+                new SuperInitializer(superTarget, new Arguments.empty())
+                  ..isSynthetic = true;
           }
           constructor.initializers.add(initializer);
           initializer.parent = constructor;
         }
         if (constructor.function.body == null) {
           /// >If a generative constructor c is not a redirecting constructor
           /// >and no body is provided, then c implicitly has an empty body {}.
           /// We use an empty statement instead.
           constructor.function.body = new EmptyStatement();
           constructor.function.body.parent = constructor.function;
@@ skipping 34 matching lines @@
       }
     }
     // Run through all fields that are initialized by some constructor, and
     // make sure that all other constructors also initialize them.
     fieldInitializers.forEach(
         (Constructor constructor, List<FieldInitializer> initializers) {
       Iterable<Field> fields = initializers.map((i) => i.field);
       for (Field field in initializedFields.difference(fields.toSet())) {
         if (field.initializer == null) {
           FieldInitializer initializer =
-              new FieldInitializer(field, new NullLiteral());
+              new FieldInitializer(field, new NullLiteral())
+                ..isSynthetic = true;
           initializer.parent = constructor;
           constructor.initializers.insert(0, initializer);
         }
       }
     });
   }
 
   /// Run all transformations that are needed when building a program for the
   /// first time.
   void runBuildTransformations() {
@@ skipping 26 matching lines @@
   }
   for (Constructor constructor in superclass.constructors) {
     if (constructor.name.name.isEmpty) {
       return constructor.function.requiredParameterCount == 0
           ? constructor
           : null;
     }
   }
   return null;
 }