Use entities in js_emitter/model.dart

pkg/compiler/lib/src/js_emitter/native_emitter.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 dart2js.js_emitter.native_emitter;
 
 import '../common.dart';
 import '../compiler.dart' show Compiler;
 import '../elements/resolution_types.dart'
     show ResolutionDartType, ResolutionFunctionType;
@@ skipping 157 matching lines @@
       }
     }
 
     // Collect all the tags that map to each native class.
 
     Map<Class, Set<String>> leafTags = new Map<Class, Set<String>>();
     Map<Class, Set<String>> nonleafTags = new Map<Class, Set<String>>();
 
     for (Class cls in classes) {
       if (!cls.isNative) continue;
-      if (backend.isJsInterop(cls.element)) continue;
+      ClassElement element = cls.element;
+      if (backend.isJsInterop(element)) continue;
       List<String> nativeTags =
           backend.nativeData.getNativeTagsOfClass(cls.element);
 
       if (nonLeafClasses.contains(cls) || extensionPoints.containsKey(cls)) {
         nonleafTags
             .putIfAbsent(cls, () => new Set<String>())
             .addAll(nativeTags);
       } else {
         Class sufficingInterceptor = cls;
         while (!neededClasses.contains(sufficingInterceptor)) {
@@ skipping 182 matching lines @@
     // used.  We should also use an interceptor if the check can't be satisfied
     // by a native class in case we get a native instance that tries to spoof
     // the type info.  i.e the criteria for whether or not to use an interceptor
     // is whether the receiver can be native, not the type of the test.
     if (element == null || !element.isClass) return false;
     ClassElement cls = element;
     if (backend.isNativeOrExtendsNative(cls)) return true;
     return isSupertypeOfNativeClass(element);
   }
 }