Move native and js interop properties from the element model to the JS backend

pkg/compiler/lib/src/js_emitter/program_builder/collector.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.program_builder;
 
 /**
  * Generates the code for all used classes in the program. Static fields (even
  * in classes) are ignored, since they can be treated as non-class elements.
  *
@@ skipping 218 matching lines @@
       neededClasses.add(compiler.boolClass);
     }
     if (neededClasses.contains(backend.jsArrayClass)) {
       neededClasses.add(compiler.listClass);
     }
 
     // 4. Finally, sort the classes.
     List<ClassElement> sortedClasses = Elements.sortedByPosition(neededClasses);
 
     for (ClassElement element in sortedClasses) {
-      if (Elements.isNativeOrExtendsNative(element) &&
+      if (backend.isNativeOrExtendsNative(element) &&
           !classesOnlyNeededForRti.contains(element)) {
         // For now, native classes and related classes cannot be deferred.
         nativeClassesAndSubclasses.add(element);
         assert(invariant(element,
                          !compiler.deferredLoadTask.isDeferred(element)));
         outputClassLists.putIfAbsent(compiler.deferredLoadTask.mainOutputUnit,
             () => new List<ClassElement>()).add(element);
       } else {
         outputClassLists.putIfAbsent(
             compiler.deferredLoadTask.outputUnitForElement(element),
@@ skipping 54 matching lines @@
   }
 
   void collect() {
     computeNeededDeclarations();
     computeNeededConstants();
     computeNeededStatics();
     computeNeededStaticNonFinalFields();
     computeNeededLibraries();
   }
 }