Move towards using WorldImpact for codegen

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

 // 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.
 
 /// Analysis to determine how to generate code for typed JavaScript interop.
 library compiler.src.js_backend.js_interop_analysis;
 
 import '../common.dart';
 import '../constants/values.dart'
     show ConstantValue, ConstructedConstantValue, StringConstantValue;
@@ skipping 98 matching lines @@
       if (element is FunctionElement) {
         _checkFunctionParameters(element);
       }
 
       if (!element.isClass) return;
 
       ClassElement classElement = element;
 
       // Skip classes that are completely unreachable. This should only happen
       // when all of jsinterop types are unreachable from main.
-      if (!backend.compiler.closedWorld.isImplemented(classElement)) return;
+      if (!backend.compiler.openWorld.isImplemented(classElement)) return;
 
       if (!classElement.implementsInterface(helpers.jsJavaScriptObjectClass)) {
         backend.reporter.reportErrorMessage(classElement,
             MessageKind.JS_INTEROP_CLASS_CANNOT_EXTEND_DART_CLASS, {
           'cls': classElement.name,
           'superclass': classElement.superclass.name
         });
       }
 
       classElement.forEachMember((ClassElement classElement, Element member) {
@@ skipping 58 matching lines @@
   }
 
   FunctionType buildJsFunctionType() {
     // TODO(jacobr): consider using codegenWorld.isChecks to determine the
     // range of positional arguments that need to be supported by JavaScript
     // function types.
     return new FunctionType.synthesized(const DynamicType(), [],
         new List<DartType>.filled(16, const DynamicType()));
   }
 }