Add KernelCodegenWorkItem stub

pkg/compiler/lib/src/inferrer/inferrer_engine.dart

 // Copyright (c) 2017, 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.
 
 import 'package:kernel/ast.dart' as ir;
 
 import '../common.dart';
 import '../common/names.dart';
 import '../compiler.dart';
 import '../constants/expressions.dart';
@@ skipping 28 matching lines @@
 
 /**
  * An inferencing engine that computes a call graph of
  * [TypeInformation] nodes by visiting the AST of the application, and
  * then does the inferencing on the graph.
  */
 class InferrerEngine {
   final Map<Element, TypeInformation> defaultTypeOfParameter =
       new Map<Element, TypeInformation>();
   final WorkQueue workQueue = new WorkQueue();
-  final Element mainElement;
+  final FunctionEntity mainElement;
   final Set<Element> analyzedElements = new Set<Element>();
 
   /// The maximum number of times we allow a node in the graph to
   /// change types. If a node reaches that limit, we give up
   /// inferencing on it and give it the dynamic type.
   final int MAX_CHANGE_COUNT = 6;
 
   int overallRefineCount = 0;
   int addedInGraph = 0;
 
@@ skipping 1024 matching lines @@
   /**
    * Records that the captured variable [local] is read.
    */
   void recordCapturedLocalRead(Local local) {}
 
   /**
    * Records that the variable [local] is being updated.
    */
   void recordLocalUpdate(Local local, TypeInformation type) {}
 }