Deal with the JS helper separately from the 'native' keyword.

lib/compiler/implementation/native_handler.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('native');
 #import('dart:uri');
 #import('leg.dart');
 #import('elements/elements.dart');
 #import('js_backend/js_backend.dart');
 #import('scanner/scannerlib.dart');
@@ skipping 63 matching lines @@
 }
 
 void maybeEnableNative(Compiler compiler,
                        LibraryElement library,
                        Uri uri) {
   String libraryName = uri.toString();
   if (library.entryCompilationUnit.script.name.contains(
           'dart/tests/compiler/dart2js_native')
       || libraryName == 'dart:dom_deprecated'
       || libraryName == 'dart:isolate'
-      || libraryName == 'dart:math'
       || libraryName == 'dart:html') {
     library.canUseNative = true;
-    library.addToScope(compiler.findHelper(const SourceString('JS')), compiler);
-    if (compiler.jsIndexingBehaviorInterface !== null) {
-      library.addToScope(compiler.jsIndexingBehaviorInterface, compiler);
-    }
   }
 }
 
 void checkAllowedLibrary(ElementListener listener, Token token) {
   LibraryElement currentLibrary = listener.compilationUnitElement.getLibrary();
   if (!currentLibrary.canUseNative) {
     listener.recoverableError("Unexpected token", token: token);
   }
 }
 
@@ skipping 233 matching lines @@
                                       String parameters) {
   buffer.add("  if (Object.getPrototypeOf(this).hasOwnProperty");
   buffer.add("('$methodName')) {\n");
   buffer.add("  $code");
   buffer.add("  } else {\n");
   buffer.add("    return Object.prototype.$methodName.call(this");
   buffer.add(parameters == '' ? '' : ', $parameters');
   buffer.add(");\n");
   buffer.add("  }\n");
 }