Add FunctionEntity.asyncMarker and refactor SourceInformationStrategy to avoid ResolvedAst

pkg/compiler/lib/src/resolution/members.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.members;
 
 import 'package:front_end/src/fasta/scanner.dart' show isUserDefinableOperator;
 
 import '../common.dart';
 import '../common/names.dart' show Selectors;
 import '../common/resolution.dart' show Resolution;
 import '../compile_time_constants.dart';
 import '../constants/constructors.dart'
     show RedirectingFactoryConstantConstructor;
 import '../constants/expressions.dart';
 import '../constants/values.dart';
 import '../common_elements.dart';
 import '../elements/elements.dart';
+import '../elements/entities.dart' show AsyncMarker;
 import '../elements/modelx.dart'
     show
         ConstructorElementX,
         ErroneousElementX,
         FunctionElementX,
         JumpTargetX,
         LocalFunctionElementX,
         LocalParameterElementX,
         ParameterElementX,
         VariableElementX,
@@ skipping 4774 matching lines @@
     }
     return const NoneResult();
   }
 }
 
 /// Looks up [name] in [scope] and unwraps the result.
 Element lookupInScope(
     DiagnosticReporter reporter, Node node, Scope scope, String name) {
   return Elements.unwrap(scope.lookup(name), reporter, node);
 }