Support native extensions for analysis and docgen.

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 '../constants/values.dart';
 import '../dart2jslib.dart';
 import '../dart_types.dart';
 import '../elements/elements.dart';
-import '../elements/modelx.dart' show ClassElementX, FunctionElementX;
+import '../elements/modelx.dart'
+    show ClassElementX, FunctionElementX, LibraryElementX;
 import '../js/js.dart' as js;
 import '../js_backend/js_backend.dart';
 import '../js_emitter/js_emitter.dart' show CodeEmitterTask;
 import '../resolution/resolution.dart' show ResolverVisitor;
 import '../scanner/scannerlib.dart';
 import '../ssa/ssa.dart';
 import '../tree/tree.dart';
 import '../universe/universe.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,
-                       LibraryElement library) {
+                       LibraryElementX library) {
   String libraryName = library.canonicalUri.toString();
   if (library.entryCompilationUnit.script.name.contains(
           'dart/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') {
+      || libraryName == 'dart:web_sql'
+      || compiler.allowNativeExtensions) {
     library.canUseNative = true;
   }
 }
 
 // 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');