Add FunctionEntity.asyncMarker and refactor SourceInformationStrategy to avoid ResolvedAst

pkg/compiler/lib/src/resolution/resolution_common.dart

 // Copyright (c) 2015, 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.resolution.common;
 
 import '../common.dart';
 import '../common/resolution.dart' show Resolution;
 import '../elements/elements.dart';
+import '../elements/entities.dart' show AsyncMarker;
 import '../enqueue.dart' show DeferredAction;
 import '../tree/tree.dart';
 import 'registry.dart' show ResolutionRegistry;
 import 'scope.dart' show Scope;
 import 'type_resolver.dart' show TypeResolver;
 
 class CommonResolverVisitor<R> extends Visitor<R> {
   final Resolution resolution;
 
   CommonResolverVisitor(this.resolution);
@@ skipping 73 matching lines @@
       String name, Spannable definition, Spannable existing) {
     reporter.reportError(
         reporter.createMessage(
             definition, MessageKind.DUPLICATE_DEFINITION, {'name': name}),
         <DiagnosticMessage>[
           reporter.createMessage(
               existing, MessageKind.EXISTING_DEFINITION, {'name': name}),
         ]);
   }
 }