Add equivalence check of NativeData and InterceptorData

pkg/compiler/lib/src/js_backend/interceptor_data.dart

Index: pkg/compiler/lib/src/js_backend/interceptor_data.dart
diff --git a/pkg/compiler/lib/src/js_backend/interceptor_data.dart b/pkg/compiler/lib/src/js_backend/interceptor_data.dart
index 7a3d2dec39237347067d2a898a3a1566df0052ee..f22802f750c9796ac74acf3004de470974dc8cde 100644
--- a/pkg/compiler/lib/src/js_backend/interceptor_data.dart
+++ b/pkg/compiler/lib/src/js_backend/interceptor_data.dart
@@ -204,6 +204,12 @@ class InterceptorDataImpl implements InterceptorData {
 
   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.