Add model test of CodegenWorldBuilder to compile_from_dill_test

pkg/compiler/lib/src/universe/codegen_world_builder.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.
 
 part of world_builder;
 
 /// World builder specific to codegen.
 ///
 /// This adds additional access to liveness of selectors and elements.
 abstract class CodegenWorldBuilder implements WorldBuilder {
@@ skipping 79 matching lines @@
   final Map<String, Map<Selector, SelectorConstraints>> _invokedNames =
       <String, Map<Selector, SelectorConstraints>>{};
   final Map<String, Map<Selector, SelectorConstraints>> _invokedGetters =
       <String, Map<Selector, SelectorConstraints>>{};
   final Map<String, Map<Selector, SelectorConstraints>> _invokedSetters =
       <String, Map<Selector, SelectorConstraints>>{};
 
   final Map<ClassEntity, _ClassUsage> _processedClasses =
       <ClassEntity, _ClassUsage>{};
 
+  Map<ClassEntity, _ClassUsage> get classUsageForTesting => _processedClasses;
+
   /// Map of registered usage of static members of live classes.
   final Map<Entity, _StaticMemberUsage> _staticMemberUsage =
       <Entity, _StaticMemberUsage>{};
 
+  Map<Entity, _StaticMemberUsage> get staticMemberUsageForTesting =>
+      _staticMemberUsage;
+
   /// Map of registered usage of instance members of live classes.
   final Map<MemberEntity, _MemberUsage> _instanceMemberUsage =
       <MemberEntity, _MemberUsage>{};
 
+  Map<MemberEntity, _MemberUsage> get instanceMemberUsageForTesting =>
+      _instanceMemberUsage;
+
   /// Map containing instance members of live classes that are not yet live
   /// themselves.
   final Map<String, Set<_MemberUsage>> _instanceMembersByName =
       <String, Set<_MemberUsage>>{};
 
   /// Map containing instance methods of live classes that are not yet
   /// closurized.
   final Map<String, Set<_MemberUsage>> _instanceFunctionsByName =
       <String, Set<_MemberUsage>>{};
 
@@ skipping 455 matching lines @@
     throw new UnimplementedError('KernelCodegenWorldBuilder.forEachParameter');
   }
 
   @override
   void forEachInstanceField(
       ClassEntity cls, void f(ClassEntity declarer, FieldEntity field)) {
     throw new UnimplementedError(
         'KernelCodegenWorldBuilder.forEachInstanceField');
   }
 }