Introduce BackendImpact to separate enqueueing from data.

pkg/compiler/lib/src/js_backend/backend_helpers.dart

Index: pkg/compiler/lib/src/js_backend/backend_helpers.dart
diff --git a/pkg/compiler/lib/src/js_backend/backend_helpers.dart b/pkg/compiler/lib/src/js_backend/backend_helpers.dart
new file mode 100644
index 0000000000000000000000000000000000000000..3c5989186d668fa3dee996cb0e33ab00154b968c
--- /dev/null
+++ b/pkg/compiler/lib/src/js_backend/backend_helpers.dart
@@ -0,0 +1,262 @@
+// 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.
+
+library dart2js.js_backend.helpers;
+
+import '../common/resolution.dart' show
+    Resolution;
+import '../compiler.dart' show
+    Compiler;
+import '../elements/elements.dart' show
+    ClassElement,
+    Element,
+    LibraryElement,
+    MethodElement;
+
+import 'js_backend.dart';
+
+/// Helper classes and functions for the JavaScript backend.
+class BackendHelpers {
+  final Compiler compiler;
+
+  Element cachedCheckConcurrentModificationError;
+
+  BackendHelpers(this.compiler);
+
+  JavaScriptBackend get backend => compiler.backend;
+
+  Resolution get resolution => backend.resolution;
+
+  MethodElement assertTest;
+  MethodElement assertThrow;
+  MethodElement assertHelper;
+
+  Element findHelper(String name) => backend.findHelper(name);
+  Element findAsyncHelper(String name) => backend.findAsyncHelper(name);
+  Element findInterceptor(String name) => backend.findInterceptor(name);
+
+  Element find(LibraryElement library, String name) {
+    return backend.find(library, name);
+  }
+
+  Element get exceptionUnwrapper {
+    return findHelper('unwrapException');
+  }
+
+  Element get throwRuntimeError {
+    return findHelper('throwRuntimeError');
+  }
+
+  Element get throwTypeError {
+    return findHelper('throwTypeError');
+  }
+
+  Element get throwAbstractClassInstantiationError {
+    return findHelper('throwAbstractClassInstantiationError');
+  }
+
+  Element get checkConcurrentModificationError {
+    if (cachedCheckConcurrentModificationError == null) {
+      cachedCheckConcurrentModificationError =
+          findHelper('checkConcurrentModificationError');
+    }
+    return cachedCheckConcurrentModificationError;
+  }
+
+  Element get throwConcurrentModificationError {
+    return findHelper('throwConcurrentModificationError');
+  }
+
+  Element get throwIndexOutOfBoundsError {
+    return findHelper('ioore');
+  }
+
+  Element get stringInterpolationHelper {
+    return findHelper('S');
+  }
+
+  Element get wrapExceptionHelper {
+    return findHelper(r'wrapException');
+  }
+
+  Element get throwExpressionHelper {
+    return findHelper('throwExpression');
+  }
+
+  Element get closureConverter {
+    return findHelper('convertDartClosureToJS');
+  }
+
+  Element get traceFromException {
+    return findHelper('getTraceFromException');
+  }
+
+  Element get setRuntimeTypeInfo {
+    return findHelper('setRuntimeTypeInfo');
+  }
+
+  Element get getRuntimeTypeInfo {
+    return findHelper('getRuntimeTypeInfo');
+  }
+
+  Element get getTypeArgumentByIndex {
+    return findHelper('getTypeArgumentByIndex');
+  }
+
+  Element get copyTypeArguments {
+    return findHelper('copyTypeArguments');
+  }
+
+  Element get computeSignature {
+    return findHelper('computeSignature');
+  }
+
+  Element get getRuntimeTypeArguments {
+    return findHelper('getRuntimeTypeArguments');
+  }
+
+  Element get getRuntimeTypeArgument {
+    return findHelper('getRuntimeTypeArgument');
+  }
+
+  Element get runtimeTypeToString {
+    return findHelper('runtimeTypeToString');
+  }
+
+  Element get assertIsSubtype {
+    return findHelper('assertIsSubtype');
+  }
+
+  Element get checkSubtype {
+    return findHelper('checkSubtype');
+  }
+
+  Element get assertSubtype {
+    return findHelper('assertSubtype');
+  }
+
+  Element get subtypeCast {
+    return findHelper('subtypeCast');
+  }
+
+  Element get checkSubtypeOfRuntimeType {
+    return findHelper('checkSubtypeOfRuntimeType');
+  }
+
+  Element get assertSubtypeOfRuntimeType {
+    return findHelper('assertSubtypeOfRuntimeType');
+  }
+
+  Element get subtypeOfRuntimeTypeCast {
+    return findHelper('subtypeOfRuntimeTypeCast');
+  }
+
+  Element get checkDeferredIsLoaded {
+    return findHelper('checkDeferredIsLoaded');
+  }
+
+  Element get throwNoSuchMethod {
+    return findHelper('throwNoSuchMethod');
+  }
+
+  Element get createRuntimeType {
+    return findHelper('createRuntimeType');
+  }
+
+  Element get fallThroughError {
+    return findHelper("getFallThroughError");
+  }
+
+  Element get createInvocationMirror {
+    return findHelper(Compiler.CREATE_INVOCATION_MIRROR);
+  }
+
+  Element get cyclicThrowHelper {
+    return findHelper("throwCyclicInit");
+  }
+
+  Element get asyncHelper {
+    return findAsyncHelper("_asyncHelper");
+  }
+
+  Element get wrapBody {
+    return findAsyncHelper("_wrapJsFunctionForAsync");
+  }
+
+  Element get yieldStar {
+    ClassElement classElement = findAsyncHelper("_IterationMarker");
+    classElement.ensureResolved(resolution);
+    return classElement.lookupLocalMember("yieldStar");
+  }
+
+  Element get yieldSingle {
+    ClassElement classElement = findAsyncHelper("_IterationMarker");
+    classElement.ensureResolved(resolution);
+    return classElement.lookupLocalMember("yieldSingle");
+  }
+
+  Element get syncStarUncaughtError {
+    ClassElement classElement = findAsyncHelper("_IterationMarker");
+    classElement.ensureResolved(resolution);
+    return classElement.lookupLocalMember("uncaughtError");
+  }
+
+  Element get asyncStarHelper {
+    return findAsyncHelper("_asyncStarHelper");
+  }
+
+  Element get streamOfController {
+    return findAsyncHelper("_streamOfController");
+  }
+
+  Element get endOfIteration {
+    ClassElement classElement = findAsyncHelper("_IterationMarker");
+    classElement.ensureResolved(resolution);
+    return classElement.lookupLocalMember("endOfIteration");
+  }
+
+  Element get syncStarIterable {
+    ClassElement classElement = findAsyncHelper("_SyncStarIterable");
+    classElement.ensureResolved(resolution);
+    return classElement;
+  }
+
+  Element get syncStarIterableConstructor {
+    ClassElement classElement = syncStarIterable;
+    classElement.ensureResolved(resolution);
+    return classElement.lookupConstructor("");
+  }
+
+  Element get syncCompleterConstructor {
+    ClassElement classElement = find(compiler.asyncLibrary, "Completer");
+    classElement.ensureResolved(resolution);
+    return classElement.lookupConstructor("sync");
+  }
+
+  Element get asyncStarController {
+    ClassElement classElement =
+        findAsyncHelper("_AsyncStarStreamController");
+    classElement.ensureResolved(resolution);
+    return classElement;
+  }
+
+  Element get asyncStarControllerConstructor {
+    ClassElement classElement = asyncStarController;
+    return classElement.lookupConstructor("");
+  }
+
+  Element get streamIteratorConstructor {
+    ClassElement classElement = find(compiler.asyncLibrary, "StreamIterator");
+    classElement.ensureResolved(resolution);
+    return classElement.lookupConstructor("");
+  }
+
+  MethodElement get functionTypeTestMetaHelper {
+    return findHelper('functionTypeTestMetaHelper');
+  }
+
+  MethodElement get defineProperty {
+    return findHelper('defineProperty');
+  }
+}