Decouple WorkItem from Compiler

tests/compiler/dart2js/exit_code_test.dart

Index: tests/compiler/dart2js/exit_code_test.dart
diff --git a/tests/compiler/dart2js/exit_code_test.dart b/tests/compiler/dart2js/exit_code_test.dart
index 1ca76fcb32f16ba2362fd6f437b4f849cd0ed833..8478d429ebb34d027b8e56fcc876274d8b78704a 100644
--- a/tests/compiler/dart2js/exit_code_test.dart
+++ b/tests/compiler/dart2js/exit_code_test.dart
@@ -11,7 +11,9 @@ import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
 
 import 'package:compiler/compiler_new.dart' as api;
+import 'package:compiler/src/common/backend_api.dart';
 import 'package:compiler/src/common/codegen.dart';
+import 'package:compiler/src/common/resolution.dart';
 import 'package:compiler/src/compile_time_constants.dart';
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/dart2js.dart' as entry;
@@ -20,8 +22,8 @@ import 'package:compiler/src/diagnostics/invariant.dart';
 import 'package:compiler/src/diagnostics/messages.dart';
 import 'package:compiler/src/diagnostics/spannable.dart';
 import 'package:compiler/src/apiimpl.dart' as apiimpl;
-import 'package:compiler/src/enqueue.dart';
 import 'package:compiler/src/elements/elements.dart';
+import 'package:compiler/src/js_backend/js_backend.dart';
 import 'package:compiler/src/library_loader.dart';
 import 'package:compiler/src/null_compiler_output.dart';
 import 'package:compiler/src/options.dart' show CompilerOptions;
@@ -52,9 +54,17 @@ class TestCompiler extends apiimpl.CompilerImpl {
   }
 
   @override
+  Backend createBackend() {
+    return new TestBackend(this);
+  }
+
+  @override
   ScannerTask createScannerTask() => new TestScanner(this);
 
   @override
+  Resolution createResolution() => new TestResolution(this);
+
+  @override
   ResolverTask createResolverTask() {
     return new TestResolver(this, backend.constantCompilerTask);
   }
@@ -74,16 +84,6 @@ class TestCompiler extends apiimpl.CompilerImpl {
     return super.onLibrariesLoaded(loadedLibraries);
   }
 
-  WorldImpact analyzeElement(Element element) {
-    test('Compiler.analyzeElement');
-    return super.analyzeElement(element);
-  }
-
-  WorldImpact codegen(CodegenWorkItem work, Enqueuer world) {
-    test('Compiler.codegen');
-    return super.codegen(work, world);
-  }
-
   test(String marker) {
     if (marker == testMarker) {
       switch (testType) {
@@ -121,6 +121,23 @@ class TestCompiler extends apiimpl.CompilerImpl {
   }
 }
 
+class TestBackend extends JavaScriptBackend {
+  final TestCompiler compiler;
+  TestBackend(TestCompiler compiler)
+      : this.compiler = compiler,
+        super(compiler,
+            generateSourceMap: compiler.options.generateSourceMap,
+            useStartupEmitter: compiler.options.useStartupEmitter,
+            useNewSourceInfo: compiler.options.useNewSourceInfo,
+            useKernel: compiler.options.useKernel);
+
+  @override
+  WorldImpact codegen(CodegenWorkItem work) {
+    compiler.test('Compiler.codegen');
+    return super.codegen(work);
+  }
+}
+
 class TestDiagnosticReporter extends DiagnosticReporterWrapper {
   TestCompiler compiler;
   DiagnosticReporter reporter;
@@ -161,6 +178,20 @@ class TestResolver extends ResolverTask {
   }
 }
 
+class TestResolution extends CompilerResolution {
+  TestCompiler compiler;
+
+  TestResolution(TestCompiler compiler)
+      : this.compiler = compiler,
+        super(compiler);
+
+  @override
+  WorldImpact computeWorldImpact(Element element) {
+    compiler.test('Compiler.analyzeElement');
+    return super.computeWorldImpact(element);
+  }
+}
+
 int checkedResults = 0;
 
 Future testExitCode(