Assert that we don't mix K and J elements

pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.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.
 
 part of dart2js.js_emitter.startup_emitter.model_emitter;
 
 /// The name of the property that stores the tear-off getter on a static
 /// function.
 ///
 /// This property is only used when isolates are used.
@@ skipping 523 matching lines @@
       'inheritance': emitInheritance(fragment),
       'aliases': emitInstanceMethodAliases(fragment),
       'tearOffs': emitInstallTearOffs(fragment),
       'constants': emitConstants(fragment),
       'staticNonFinalFields': emitStaticNonFinalFields(fragment),
       'lazyStatics': emitLazilyInitializedStatics(fragment),
       'embeddedGlobals': emitEmbeddedGlobals(program, deferredLoadHashes),
       'nativeSupport': program.needsNativeSupport
           ? emitNativeSupport(fragment)
           : new js.EmptyStatement(),
-      'jsInteropSupport': backend.nativeBasicData.isJsInteropUsed
+      'jsInteropSupport': _closedWorld.nativeData.isJsInteropUsed
           ? backend.jsInteropAnalysis.buildJsInteropBootstrap()
           : new js.EmptyStatement(),
       'invokeMain': fragment.invokeMain,
     });
     if (program.hasSoftDeferredClasses) {
       return new js.Block([
         js.js.statement(softDeferredBoilerplate, {
           'deferredGlobal': ModelEmitter.deferredInitializersGlobal,
           'softId': js.string(softDeferredId),
           // TODO(floitsch): don't just reference 'init'.
@@ skipping 998 matching lines @@
     }
     statements.add(js.js.statement("setOrUpdateInterceptorsByTag(#);",
         js.objectLiteral(interceptorsByTag)));
     statements.add(
         js.js.statement("setOrUpdateLeafTags(#);", js.objectLiteral(leafTags)));
     statements.addAll(subclassAssignments);
 
     return wrapPhase('nativeSupport', statements);
   }
 }