Implement LibraryElement.hasExtUri for resynthesized.

pkg/analyzer/test/generated/non_error_resolver_driver_test.dart

 // Copyright (c) 2017, 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.
 
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import 'non_error_resolver_test.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(NonErrorResolverTest_Driver);
   });
 }
 
 @reflectiveTest
 class NonErrorResolverTest_Driver extends NonErrorResolverTest {
   @override
   bool get enableNewAnalysisDriver => true;
-
-  @failingTest
-  @override
-  test_nativeConstConstructor() {
-    return super.test_nativeConstConstructor();
-  }
-
-  @failingTest
-  @override
-  test_nativeFunctionBodyInNonSDKCode_function() {
-    return super.test_nativeFunctionBodyInNonSDKCode_function();
-  }
 }