Introduce BackendImpact to separate enqueueing from data.

pkg/compiler/lib/src/js_emitter/lazy_emitter/model_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.lazy_emitter.model_emitter;
 
 import '../../compiler.dart' show
     Compiler;
 import '../../constants/values.dart' show
     ConstantValue,
@@ skipping 195 matching lines @@
       {'deferredInitializer': emitDeferredInitializerGlobal(program.loadMap),
        'holders': emitHolders(program.holders),
        'tearOff': buildTearOffCode(backend),
        'parseFunctionDescriptor':
            js.js.statement(parseFunctionDescriptorBoilerplate,
                {'argumentCount': js.string(namer.requiredParameterField),
                 'defaultArgumentValues': js.string(namer.defaultValuesField),
                 'callName': js.string(namer.callNameField)}),
 
        'cyclicThrow':
-           backend.emitter.staticFunctionAccess(backend.getCyclicThrowHelper()),
+           backend.emitter.staticFunctionAccess(
+               backend.helpers.cyclicThrowHelper),
        'outputContainsConstantList': program.outputContainsConstantList,
        'embeddedGlobals': emitEmbeddedGlobals(program),
        'readMetadataTypeFunction': readMetadataTypeFunction,
        'staticNonFinals':
             emitStaticNonFinalFields(fragment.staticNonFinalFields),
        'operatorIsPrefix': js.string(namer.operatorIsPrefix),
        'callName': js.string(namer.callNameField),
        'argumentCount': js.string(namer.requiredParameterField),
        'defaultArgumentValues': js.string(namer.defaultValuesField),
        'eagerClasses': emitEagerClassInitializations(fragment.libraries),
@@ skipping 1017 matching lines @@
 
   var end = Date.now();
   // print('Setup: ' + (end - start) + ' ms.');
 
   #invokeMain;  // Start main.
 
 })(Date.now(), #code)
 }""";
 
 }