Expand ResolvedAst to handle synthetic constructors.

pkg/compiler/lib/src/common/backend_api.dart

 // Copyright (c) 2012, 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 dart2js.backend_api;
 
 import 'dart:async' show Future;
 
 import '../common.dart';
 import '../common/codegen.dart' show CodegenImpact;
@@ skipping 343 matching lines @@
   }
 
   /// Called after the queue is closed. [onQueueEmpty] may be called multiple
   /// times, but [onQueueClosed] is only called once.
   void onQueueClosed() {}
 
   /// Called when the compiler starts running the codegen enqueuer.
   void onCodegenStart() {}
 
   /// Called after [element] has been resolved.
-  // TODO(johnniwinther): Change [TreeElements] to [Registry] or a dependency
-  // node. [elements] is currently unused by the implementation.
-  void onElementResolved(Element element, TreeElements elements) {}
+  void onElementResolved(Element element) {}
 
   // Does this element belong in the output
   bool shouldOutput(Element element) => true;
 
   FunctionElement helperForBadMain() => null;
 
   FunctionElement helperForMissingMain() => null;
 
   FunctionElement helperForMainArity() => null;
 
@@ skipping 51 matching lines @@
   }
 }
 
 /// Interface for serialization of backend specific data.
 class BackendSerialization {
   const BackendSerialization();
 
   SerializerPlugin get serializer => const SerializerPlugin();
   DeserializerPlugin get deserializer => const DeserializerPlugin();
 }