Decouple WorkItem from Compiler

tests/compiler/dart2js/compiler_helper.dart

Index: tests/compiler/dart2js/compiler_helper.dart
diff --git a/tests/compiler/dart2js/compiler_helper.dart b/tests/compiler/dart2js/compiler_helper.dart
index eaa26df0ac9d44932553f86ccecdcf8760a3775a..ff3dffaed20c952c92c164f9e89267ac77780693 100644
--- a/tests/compiler/dart2js/compiler_helper.dart
+++ b/tests/compiler/dart2js/compiler_helper.dart
@@ -72,15 +72,17 @@ Future<String> compile(String code,
     lego.Element element = compiler.mainApp.find(entry);
     if (element == null) return null;
     compiler.phase = Compiler.PHASE_RESOLVING;
-    compiler.backend.enqueueHelpers(compiler.enqueuer.resolution);
+    compiler.enqueuer.resolution
+        .applyImpact(compiler.backend.computeHelpersImpact());
     compiler.processQueue(compiler.enqueuer.resolution, element);
     compiler.openWorld.closeWorld(compiler.reporter);
     compiler.backend.onResolutionComplete();
-    ResolutionWorkItem resolutionWork = new ResolutionWorkItem(element);
-    resolutionWork.run(compiler, compiler.enqueuer.resolution);
-    CodegenWorkItem work = new CodegenWorkItem(compiler, element);
+    ResolutionWorkItem resolutionWork =
+        new ResolutionWorkItem(compiler.resolution, element);
+    resolutionWork.run();
+    CodegenWorkItem work = new CodegenWorkItem(compiler.backend, element);
     compiler.phase = Compiler.PHASE_COMPILING;
-    work.run(compiler, compiler.enqueuer.codegen);
+    work.run();
     js.JavaScriptBackend backend = compiler.backend;
     String generated = backend.getGeneratedCode(element);
     if (check != null) {