Remove dart:jni library in FlutterTarget

pkg/kernel/lib/target/flutter.dart

 // Copyright (c) 2016, 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 kernel.target.flutter;
 
 import '../ast.dart';
 import '../transformations/continuation.dart' as cont;
 import '../transformations/erasure.dart';
 import '../transformations/sanitize_for_vm.dart';
 import '../transformations/mixin_full_resolution.dart' as mix;
@@ skipping 28 matching lines @@
 
         'dart:profiler',
         'dart:typed_data',
         'dart:_vmservice',
         'dart:_builtin',
         'dart:nativewrappers',
         'dart:io',
 
         // Required for flutter.
         'dart:ui',
-        'dart:jni',
         'dart:vmservice_sky',
       ];
 
   void performModularTransformations(Program program) {
     new mix.MixinFullResolution().transform(program);
   }
 
   void performGlobalTransformations(Program program) {
     cont.transformProgram(program);
 
     // Repair `_getMainClosure()` function in dart:{_builtin,ui} libraries.
     setup_builtin_library.transformProgram(program);
     setup_builtin_library.transformProgram(program, libraryUri: 'dart:ui');
 
     if (strongMode) {
       new Erasure().transform(program);
     }
 
     new SanitizeForVM().transform(program);
   }
 }