Add equivalence check of NativeData and InterceptorData

pkg/compiler/lib/src/js_backend/interceptor_data.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.
 
 library js_backend.interceptor_data;
 
 import '../common/names.dart' show Identifiers;
 import '../common_elements.dart' show CommonElements, ElementEnvironment;
 import '../elements/elements.dart' show MemberElement;
 import '../elements/entities.dart';
@@ skipping 186 matching lines @@
     if (interceptedClasses.contains(element)) return true;
     if (_classesMixedIntoInterceptedClasses.contains(element)) return true;
     return false;
   }
 
   bool isMixedIntoInterceptedClass(ClassEntity element) =>
       _classesMixedIntoInterceptedClasses.contains(element);
 
   Iterable<ClassEntity> get interceptedClasses => _interceptedClasses;
 
+  Map<String, Set<MemberEntity>> get interceptedElementsForTesting =>
+      _interceptedElements;
+
+  Set<ClassEntity> get classesMixedIntoInterceptedClassesForTesting =>
+      _classesMixedIntoInterceptedClasses;
+
   bool mayGenerateInstanceofCheck(DartType type, ClosedWorld closedWorld) {
     // We can use an instanceof check for raw types that have no subclass that
     // is mixed-in or in an implements clause.
 
     if (!type.treatAsRaw) return false;
     InterfaceType interfaceType = type;
     ClassEntity classElement = interfaceType.element;
     if (isInterceptedClass(classElement)) return false;
     return closedWorld.hasOnlySubclasses(classElement);
   }
@@ skipping 111 matching lines @@
     jsAst.Name name = namer.nameForGetInterceptor(classes);
     if (classes.contains(_commonElements.jsInterceptorClass)) {
       // We can't use a specialized [getInterceptorMethod], so we make
       // sure we emit the one with all checks.
       _specializedGetInterceptors[name] = _interceptorData.interceptedClasses;
     } else {
       _specializedGetInterceptors[name] = classes;
     }
   }
 }