Support deserialized compilation of the empty program.

pkg/compiler/lib/src/common/backend_api.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.backend_api;
 
 import 'dart:async' show Future;
 
 import '../common.dart';
 import '../common/codegen.dart' show CodegenImpact;
-import '../common/resolution.dart' show ResolutionImpact;
+import '../common/resolution.dart' show ResolutionImpact, Frontend;
 import '../compile_time_constants.dart'
     show BackendConstantEnvironment, ConstantCompilerTask;
 import '../compiler.dart' show Compiler;
 import '../constants/constant_system.dart' show ConstantSystem;
 import '../constants/expressions.dart' show ConstantExpression;
 import '../constants/values.dart' show ConstantValue;
 import '../dart_types.dart' show DartType, InterfaceType;
 import '../elements/elements.dart'
     show
         ClassElement,
@@ skipping 364 matching lines @@
   /// Returns null if there is none.
   Uri resolvePatchUri(String libraryName, Uri plaformConfigUri);
 
   /// Creates an impact strategy to use for compilation.
   ImpactStrategy createImpactStrategy(
       {bool supportDeferredLoad: true,
       bool supportDumpInfo: true,
       bool supportSerialization: true}) {
     return const ImpactStrategy();
   }
+
+  /// Backend access to the front-end.
+  Frontend get frontend => compiler.resolution;
 }
 
 /// Interface for resolving calls to foreign functions.
 abstract class ForeignResolver {
   /// Returns the constant expression of [node], or `null` if [node] is not
   /// a constant expression.
   ConstantExpression getConstant(Node node);
 
   /// Registers [type] as instantiated.
   void registerInstantiatedType(InterfaceType type);
@@ skipping 17 matching lines @@
   }
 }
 
 /// Interface for serialization of backend specific data.
 class BackendSerialization {
   const BackendSerialization();
 
   SerializerPlugin get serializer => const SerializerPlugin();
   DeserializerPlugin get deserializer => const DeserializerPlugin();
 }