Add FunctionEntity.asyncMarker and refactor SourceInformationStrategy to avoid ResolvedAst

pkg/compiler/lib/src/resolution/resolution.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.resolution;
 
 import 'dart:collection' show Queue;
 
 import '../common.dart';
 import '../common/names.dart' show Identifiers;
 import '../common/resolution.dart'
     show ParsingContext, Resolution, ResolutionImpact, Target;
 import '../common/tasks.dart' show CompilerTask, Measurer;
 import '../compile_time_constants.dart' show ConstantCompiler;
 import '../constants/expressions.dart'
     show
         ConstantExpression,
         ConstantExpressionKind,
         ConstructedConstantExpression,
         ErroneousConstantExpression;
 import '../constants/values.dart' show ConstantValue;
 import '../common_elements.dart' show CommonElements;
 import '../elements/resolution_types.dart';
 import '../elements/elements.dart';
+import '../elements/entities.dart' show AsyncMarker;
 import '../elements/modelx.dart'
     show
         BaseClassElementX,
         BaseFunctionElementX,
         ConstructorElementX,
         FieldElementX,
         FunctionElementX,
         GetterElementX,
         MetadataAnnotationX,
         MixinApplicationElementX,
@@ skipping 1126 matching lines @@
   TreeElements get treeElements {
     assert(_treeElements != null,
         failedAt(this, "TreeElements have not been computed for $this."));
     return _treeElements;
   }
 
   void reuseElement() {
     _treeElements = null;
   }
 }