Move towards using WorldImpact for codegen

pkg/compiler/lib/src/js_emitter/program_builder/program_builder.dart

 // Copyright (c) 2014, 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.js_emitter.program_builder;
 
 import '../../closure.dart' show ClosureFieldElement;
 import '../../common.dart';
 import '../../common/names.dart' show Names, Selectors;
 import '../../compiler.dart' show Compiler;
@@ skipping 151 matching lines @@
 
     List<Fragment> fragments = new List<Fragment>(_registry.librariesMapCount);
     fragments[0] = mainFragment;
     fragments.setAll(1, deferredFragments);
 
     _markEagerClasses();
 
     List<Holder> holders = _registry.holders.toList(growable: false);
 
     bool needsNativeSupport = _compiler.enqueuer.codegen.nativeEnqueuer
-        .hasInstantiatedNativeClasses();
+        .hasInstantiatedNativeClasses;
 
     assert(!needsNativeSupport || nativeClasses.isNotEmpty);
 
     List<js.TokenFinalizer> finalizers = [_task.metadataCollector];
     if (backend.namer is js.TokenFinalizer) {
       var namingFinalizer = backend.namer;
       finalizers.add(namingFinalizer);
     }
 
     return new Program(fragments, holders, _buildLoadMap(), _symbolsMap,
@@ skipping 797 matching lines @@
       Constant constant = new Constant(name, holder, constantValue);
       _constants[constantValue] = constant;
     }
   }
 
   Holder _registerStaticStateHolder() {
     return _registry.registerHolder(namer.staticStateHolder,
         isStaticStateHolder: true);
   }
 }