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

pkg/compiler/lib/src/native/native.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:collection' show Queue;
 
 import '../common.dart';
 import '../common/backend_api.dart' show
@@ skipping 38 matching lines @@
 import '../universe/side_effects.dart' show
     SideEffects;
 import '../util/util.dart';
 
 part 'behavior.dart';
 part 'enqueue.dart';
 part 'js.dart';
 part 'scanner.dart';
 part 'ssa.dart';
 
-void maybeEnableNative(Compiler compiler,
-                       LibraryElementX library) {
+bool maybeEnableNative(Compiler compiler,
+                       LibraryElement library) {
   String libraryName = library.canonicalUri.toString();
   if (library.entryCompilationUnit.script.name.contains(
           'sdk/tests/compiler/dart2js_native')
       || libraryName == 'dart:async'
       || libraryName == 'dart:html'
       || libraryName == 'dart:html_common'
       || libraryName == 'dart:indexed_db'
       || libraryName == 'dart:js'
       || libraryName == 'dart:svg'
       || libraryName == 'dart:_native_typed_data'
       || libraryName == 'dart:web_audio'
       || libraryName == 'dart:web_gl'
       || libraryName == 'dart:web_sql'
       || compiler.allowNativeExtensions) {
-    library.canUseNative = true;
+    return true;
   }
+  return false;
 }
-
-// The tags string contains comma-separated 'words' which are either dispatch
-// tags (having JavaScript identifier syntax) and directives that begin with
-// `!`.
-List<String> nativeTagsOfClassRaw(ClassElement cls) {
-  String quotedName = cls.nativeTagInfo;
-  return quotedName.substring(1, quotedName.length - 1).split(',');
-}
-
-List<String> nativeTagsOfClass(ClassElement cls) {
-  return nativeTagsOfClassRaw(cls).where((s) => !s.startsWith('!')).toList();
-}
-
-bool nativeTagsForcedNonLeaf(ClassElement cls) =>
-    nativeTagsOfClassRaw(cls).contains('!nonleaf');