Add FunctionEntity.asyncMarker and refactor SourceInformationStrategy to avoid ResolvedAst

pkg/compiler/lib/src/kernel/kernel_backend_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.backend_strategy;
 
 import 'package:kernel/ast.dart' as ir;
 
 import '../backend_strategy.dart';
 import '../closure.dart';
@@ skipping 55 matching lines @@
       SelectorConstraintsStrategy selectorConstraintsStrategy) {
     return new KernelCodegenWorldBuilder(_compiler.elementEnvironment,
         nativeBasicData, closedWorld, selectorConstraintsStrategy);
   }
 
   @override
   SsaBuilderTask createSsaBuilderTask(JavaScriptBackend backend,
       SourceInformationStrategy sourceInformationStrategy) {
     return new KernelSsaBuilderTask(backend.compiler);
   }
+
+  @override
+  SourceInformationStrategy get sourceInformationStrategy =>
+      const SourceInformationStrategy();
 }
 
 class KernelCodegenWorkItemBuilder implements WorkItemBuilder {
   final JavaScriptBackend _backend;
   final ClosedWorld _closedWorld;
 
   KernelCodegenWorkItemBuilder(this._backend, this._closedWorld);
 
   @override
   CodegenWorkItem createWorkItem(MemberEntity entity) {
@@ skipping 30 matching lines @@
   @override
   HGraph build(CodegenWorkItem work, ClosedWorld closedWorld) {
     KernelSsaBuilder builder = new KernelSsaBuilder(
         work.element,
         _elementMap.getMemberRoot(work.element),
         _compiler,
         _elementMap,
         new KernelToTypeInferenceMapImpl(closedWorld),
         closedWorld,
         work.registry,
+        // TODO(johnniwinther): Support these:
         const KernelClosureClassMaps(),
         const SourceInformationBuilder(),
-        // TODO(johnniwinther): Support these:
         null, // Function node used as capture scope id.
         targetIsConstructorBody: false);
     return builder.build();
   }
 }
 
 class KernelToTypeInferenceMapImpl implements KernelToTypeInferenceMap {
   final ClosedWorld _closedWorld;
 
   KernelToTypeInferenceMapImpl(this._closedWorld);
@@ skipping 75 matching lines @@
   @override
   ClosureClassMap getLocalFunctionMap(Local localFunction) {
     return new ClosureClassMap(null, null, null, null);
   }
 
   @override
   ClosureClassMap getMemberMap(MemberEntity member) {
     return new ClosureClassMap(null, null, null, null);
   }
 }