Assert that we don't mix K and J elements

pkg/compiler/lib/src/js_backend/backend_serialization.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 js_backend.serialization;
 
 import '../common/backend_api.dart' show BackendSerialization;
 import '../elements/elements.dart';
 import '../elements/resolution_types.dart';
 import '../elements/types.dart';
 import '../js/js.dart' as js;
 import '../native/native.dart';
+import '../resolution/resolution_strategy.dart';
 import '../serialization/keys.dart';
 import '../serialization/serialization.dart'
     show DeserializerPlugin, ObjectDecoder, ObjectEncoder, SerializerPlugin;
 import '../universe/side_effects.dart';
 import 'js_backend.dart';
 import 'native_data.dart';
 
 const String _BACKEND_DATA_TAG = 'jsBackendData';
 const Key DART_TYPES_RETURNED = const Key('dartTypesReturned');
 const Key THIS_TYPES_RETURNED = const Key('thisTypesReturned');
@@ skipping 23 matching lines @@
 const Key NATIVE_CLASS_TAG_INFO = const Key('nativeClassTagInfo');
 const Key NATIVE_METHOD_BEHAVIOR = const Key('nativeMethodBehavior');
 const Key NATIVE_FIELD_LOAD_BEHAVIOR = const Key('nativeFieldLoadBehavior');
 const Key NATIVE_FIELD_STORE_BEHAVIOR = const Key('nativeFieldStoreBehavior');
 
 class JavaScriptBackendSerializer implements SerializerPlugin {
   final JavaScriptBackend _backend;
 
   JavaScriptBackendSerializer(this._backend);
 
-  NativeBasicDataImpl get nativeBasicData => _backend.nativeBasicData;
+  NativeBasicDataImpl get nativeBasicData =>
+      _backend.compiler.frontendStrategy.nativeBasicData;
   NativeDataBuilderImpl get nativeData => _backend.nativeDataBuilder;
 
   @override
   void onElement(Element element, ObjectEncoder createEncoder(String tag)) {
     ObjectEncoder encoder;
     ObjectEncoder getEncoder() {
       return encoder ??= createEncoder(_BACKEND_DATA_TAG);
     }
 
     String jsInteropLibraryName = nativeData.jsInteropLibraryNames[element];
@@ skipping 43 matching lines @@
   void onData(covariant NativeBehavior behavior, ObjectEncoder encoder) {
     NativeBehaviorSerialization.serializeNativeBehavior(behavior, encoder);
   }
 }
 
 class JavaScriptBackendDeserializer implements DeserializerPlugin {
   final JavaScriptBackend _backend;
 
   JavaScriptBackendDeserializer(this._backend);
 
-  NativeBasicDataBuilderImpl get nativeBasicData =>
-      _backend.nativeBasicDataBuilder;
+  NativeBasicDataBuilderImpl get nativeBasicData {
+    ResolutionFrontEndStrategy frontendStrategy =
+        _backend.compiler.frontendStrategy;
+    return frontendStrategy.nativeBasicDataBuilder;
+  }
+
   NativeDataBuilderImpl get nativeData => _backend.nativeDataBuilder;
 
   @override
   void onElement(Element element, ObjectDecoder getDecoder(String tag)) {
     ObjectDecoder decoder = getDecoder(_BACKEND_DATA_TAG);
     if (decoder != null) {
       if (element is LibraryElement) {
         String jsInteropLibraryName =
             decoder.getString(JS_INTEROP_LIBRARY_NAME, isOptional: true);
         if (jsInteropLibraryName != null) {
@@ skipping 156 matching lines @@
       behavior.codeTemplate = js.js.parseForeignJS(behavior.codeTemplateText);
     }
 
     behavior.throwBehavior =
         decoder.getEnum(THROW_BEHAVIOR, NativeThrowBehavior.values);
     behavior.isAllocation = decoder.getBool(IS_ALLOCATION);
     behavior.useGvn = decoder.getBool(USE_GVN);
     return behavior;
   }
 }