Split NativeData

pkg/compiler/lib/src/js_backend/backend_usage.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 '../common.dart';
-import '../common/resolution.dart' show Resolution;
 import '../common_elements.dart';
 import '../elements/elements.dart';
-import '../elements/entities.dart';
 import '../elements/resolution_types.dart';
-import '../universe/selector.dart';
-import '../universe/use.dart';
-import '../universe/world_impact.dart'
-    show WorldImpact, WorldImpactBuilder, WorldImpactBuilderImpl;
 import '../util/util.dart' show Setlet;
 import 'backend_helpers.dart';
 import 'backend_impact.dart';
 
 abstract class BackendUsage {
   bool get needToInitializeIsolateAffinityTag;
   bool get needToInitializeDispatchProperty;
 
   /// Returns `true` if [element] is the parameter of a function called by the
   /// backend.
@@ skipping 294 matching lines @@
     return _helperFunctionsUsed.contains(element.functionDeclaration);
   }
 
   @override
   bool isFieldUsedByBackend(FieldElement element) {
     return _helperClassesUsed.contains(element.enclosingClass);
   }
 
   Iterable<Element> get globalDependencies => _globalDependencies;
 }