Introduce BackendImpact to separate enqueueing from data.

pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart

 // Copyright (c) 2015, 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 dart2js.js_emitter.startup_emitter.model_emitter;
 
 /// The name of the property that stores the tear-off getter on a static
 /// function.
 ///
 /// This property is only used when isolates are used.
@@ skipping 426 matching lines @@
       Map<DeferredFragment, _DeferredFragmentHash> deferredLoadHashes) {
     MainFragment fragment = program.fragments.first;
 
     Iterable<Holder> nonStaticStateHolders = program.holders
         .where((Holder holder) => !holder.isStaticStateHolder);
 
     return js.js.statement(mainBoilerplate,
         {'deferredInitializer': emitDeferredInitializerGlobal(program.loadMap),
          'typeNameProperty': js.string(ModelEmitter.typeNameProperty),
          'cyclicThrow': backend.emitter.staticFunctionAccess(
-                 backend.getCyclicThrowHelper()),
+                 backend.helpers.cyclicThrowHelper),
          'operatorIsPrefix': js.string(namer.operatorIsPrefix),
          'tearOffCode': new js.Block(buildTearOffCode(backend)),
          'embeddedTypes': generateEmbeddedGlobalAccess(TYPES),
          'embeddedInterceptorTags':
              generateEmbeddedGlobalAccess(INTERCEPTORS_BY_TAG),
          'embeddedLeafTags': generateEmbeddedGlobalAccess(LEAF_TAGS),
          'embeddedGlobalsObject': js.js("init"),
          'holdersList': new js.ArrayInitializer(nonStaticStateHolders
              .map((holder) => js.js("#", holder.name))
              .toList(growable: false)),
@@ skipping 854 matching lines @@
     }
     statements.add(js.js.statement("setOrUpdateInterceptorsByTag(#);",
         js.objectLiteral(interceptorsByTag)));
     statements.add(js.js.statement("setOrUpdateLeafTags(#);",
         js.objectLiteral(leafTags)));
     statements.add(subclassAssignment);
 
     return new js.Block(statements);
   }
 }