Move main and isolate handling to enqueuer listeners.

tests/compiler/dart2js/compiler_helper.dart

 // Copyright (c) 2012, 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 compiler_helper;
 
 import 'dart:async';
 import "package:expect/expect.dart";
 
 import 'package:compiler/compiler_new.dart';
@@ skipping 56 matching lines @@
         disableTypeInference: true,
         enableMinification: minify,
         disableInlining: disableInlining,
         trustJSInteropTypeAnnotations: trustJSInteropTypeAnnotations,
         outputProvider: outputCollector);
     await compiler.init();
     compiler.parseScript(code);
     lego.Element element = compiler.mainApp.find(entry);
     if (element == null) return null;
     compiler.phase = Compiler.PHASE_RESOLVING;
-    compiler.enqueuer.resolution
-        .applyImpact(compiler.backend.computeHelpersImpact());
-    compiler.processQueue(compiler.enqueuer.resolution, element);
+    compiler.processQueue(compiler.enqueuer.resolution, element,
+        compiler.libraryLoader.libraries);
     ResolutionWorkItem resolutionWork =
         new ResolutionWorkItem(compiler.resolution, element);
     resolutionWork.run();
     compiler.closeResolution();
     CodegenWorkItem work = new CodegenWorkItem(compiler.backend, element);
     compiler.phase = Compiler.PHASE_COMPILING;
     work.run();
     js.JavaScriptBackend backend = compiler.backend;
     String generated = backend.getGeneratedCode(element);
     if (check != null) {
@@ skipping 203 matching lines @@
     }
   }
 
   return checker;
 }
 
 RegExp _directivePattern = new RegExp(
     //      \1                     \2        \3
     r'''// *(present|absent): *(?:"([^"]*)"|'([^'']*)')''',
     multiLine: true);