Introduce BackendImpact to separate enqueueing from data.

pkg/compiler/lib/src/js_emitter/full_emitter/emitter.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.full_emitter;
 
 import 'dart:convert';
 import 'dart:collection' show HashMap;
 
 import 'package:js_runtime/shared/embedded_names.dart' as embeddedNames;
@@ skipping 874 matching lines @@
         generateEmbeddedGlobalAccess(embeddedNames.ALL_CLASSES);
     jsAst.Expression getTypeFromNameAccess =
         generateEmbeddedGlobalAccess(embeddedNames.GET_TYPE_FROM_NAME);
     jsAst.Expression interceptorsByTagAccess =
         generateEmbeddedGlobalAccess(embeddedNames.INTERCEPTORS_BY_TAG);
     jsAst.Expression leafTagsAccess =
         generateEmbeddedGlobalAccess(embeddedNames.LEAF_TAGS);
     jsAst.Expression finishedClassesAccess =
         generateEmbeddedGlobalAccess(embeddedNames.FINISHED_CLASSES);
     jsAst.Expression cyclicThrow =
-        staticFunctionAccess(backend.getCyclicThrowHelper());
+        staticFunctionAccess(backend.helpers.cyclicThrowHelper);
     jsAst.Expression laziesAccess =
         generateEmbeddedGlobalAccess(embeddedNames.LAZIES);
 
     return js.statement('''
       function init() {
         $isolatePropertiesName = Object.create(null);
         #allClasses = map();
         #getTypeFromName = function(name) {return #allClasses[name];};
         #interceptorsByTag = map();
         #leafTags = map();
@@ skipping 1219 matching lines @@
     for (Element element in compiler.enqueuer.codegen.newlyEnqueuedElements) {
       if (element.isInstanceMember) {
         cachedClassBuilders.remove(element.enclosingClass);
 
         nativeEmitter.cachedBuilders.remove(element.enclosingClass);
 
       }
     }
   }
 }