Add KernelCodegenWorkItem stub

pkg/compiler/lib/src/kernel/kernel_strategy.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.
 
 library dart2js.kernel.frontend_strategy;
 
 import '../closure.dart';
 import '../backend_strategy.dart';
 import '../common.dart';
 import '../common_elements.dart';
 import '../common/backend_api.dart';
-import '../common/codegen.dart' show CodegenWorkItem;
+import '../common/codegen.dart' show CodegenRegistry, CodegenWorkItem;
 import '../common/resolution.dart';
 import '../common/tasks.dart';
 import '../common/work.dart';
 import '../elements/elements.dart';
 import '../elements/entities.dart';
 import '../elements/types.dart';
 import '../environment.dart' as env;
 import '../enqueue.dart';
 import '../frontend_strategy.dart';
 import '../js_backend/backend.dart';
@@ skipping 201 matching lines @@
   void registerTypeLiteral(DartType type) {}
 }
 
 /// Mock implementation of [MirrorsResolutionAnalysis].
 class MirrorsResolutionAnalysisImpl implements MirrorsResolutionAnalysis {
   @override
   void onQueueEmpty(Enqueuer enqueuer, Iterable<ClassEntity> recentClasses) {}
 
   @override
   MirrorsCodegenAnalysis close() {
-    throw new UnimplementedError('MirrorsResolutionAnalysisImpl.close');
+    // TODO(johnniwinther): Implement this.
+    return new MirrorsCodegenAnalysisImpl();
   }
 
   @override
   void onResolutionComplete() {}
 }
 
 /// Backend strategy that uses the kernel elements as the backend model.
 // TODO(johnniwinther): Replace this with a strategy based on the J-element
 // model.
 class KernelBackendStrategy implements BackendStrategy {
   @override
   ClosedWorldRefiner createClosedWorldRefiner(KernelClosedWorld closedWorld) {
     return closedWorld;
   }
 
   @override
   Sorter get sorter =>
       throw new UnimplementedError('KernelBackendStrategy.sorter');
 
   @override
   void convertClosures(ClosedWorldRefiner closedWorldRefiner) {
     // TODO(johnniwinther,efortuna): Compute closure classes for kernel based
     // elements.
-    throw new UnimplementedError('KernelBackendStrategy.createClosureClasses');
   }
 
   @override
   WorkItemBuilder createCodegenWorkItemBuilder(ClosedWorld closedWorld) {
     return new KernelCodegenWorkItemBuilder();
   }
 
   @override
   CodegenWorldBuilder createCodegenWorldBuilder(
       NativeBasicData nativeBasicData,
       ClosedWorld closedWorld,
       SelectorConstraintsStrategy selectorConstraintsStrategy) {
     return new KernelCodegenWorldBuilder(
         null, nativeBasicData, closedWorld, selectorConstraintsStrategy);
   }
 }
 
+class MirrorsCodegenAnalysisImpl implements MirrorsCodegenAnalysis {
+  @override
+  int get preMirrorsMethodCount {
+    throw new UnimplementedError(
+        'MirrorsCodegenAnalysisImpl.preMirrorsMethodCount');
+  }
+
+  @override
+  void onQueueEmpty(Enqueuer enqueuer, Iterable<ClassEntity> recentClasses) {
+    throw new UnimplementedError('MirrorsCodegenAnalysisImpl.onQueueEmpty');
+  }
+}
+
 class KernelCodegenWorkItemBuilder implements WorkItemBuilder {
   @override
   CodegenWorkItem createWorkItem(MemberEntity entity) {
-    throw new UnimplementedError('KernelCodegenWorkItemBuilder.createWorkItem');
+    return new KernelCodegenWorkItem(entity);
   }
 }
+
+class KernelCodegenWorkItem extends CodegenWorkItem {
+  final MemberEntity element;
+  final CodegenRegistry registry;
+
+  KernelCodegenWorkItem(this.element) : registry = new CodegenRegistry(element);
+
+  @override
+  WorldImpact run() {
+    // TODO(johnniwinther): Build SSA graph from kernel and run codegen on it.
+    return const WorldImpact();
+  }
+}