Fix x.runtimeType for native classes

sdk/lib/_internal/compiler/implementation/js_backend/backend.dart

 // Copyright (c) 2012, 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.
 
 part of js_backend;
 
 typedef void Recompile(Element element);
 
 class ReturnInfo {
   HType returnType;
@@ skipping 961 matching lines @@
   void addInterceptorsForNativeClassMembers(
       ClassElement cls, Enqueuer enqueuer) {
     if (enqueuer.isResolutionQueue) {
       cls.ensureResolved(compiler);
       cls.forEachMember((ClassElement classElement, Element member) {
           // All methods on [Object] are shadowed by [Interceptor].
           if (classElement == compiler.objectClass) return;
           Set<Element> set = interceptedElements.putIfAbsent(
               member.name, () => new Set<Element>());
           set.add(member);
+          if (classElement == jsInterceptorClass) return;
           if (!classElement.isNative()) {
             MixinApplicationElement mixinApplication = classElement;
             assert(member.getEnclosingClass() == mixinApplication.mixin);
             classesMixedIntoNativeClasses.add(mixinApplication.mixin);
           }
         },
         includeSuperMembers: true);
     }
   }
 
@@ skipping 369 matching lines @@
   }
 
   native.NativeEnqueuer nativeResolutionEnqueuer(Enqueuer world) {
     return new native.NativeResolutionEnqueuer(world, compiler);
   }
 
   native.NativeEnqueuer nativeCodegenEnqueuer(Enqueuer world) {
     return new native.NativeCodegenEnqueuer(world, compiler, emitter);
   }
 
+  ClassElement defaultSuperclass(ClassElement element) {
+    // Native classes inherit from Interceptor.
+    return element.isNative() ? jsInterceptorClass : compiler.objectClass;
+  }
+
   /**
    * Unit test hook that returns code of an element as a String.
    *
    * Invariant: [element] must be a declaration element.
    */
   String assembleCode(Element element) {
     assert(invariant(element, element.isDeclaration));
     return jsAst.prettyPrint(generatedCode[element], compiler).getText();
   }
 
@@ skipping 399 matching lines @@
   ClassElement get constListImplementation => jsArrayClass;
   ClassElement get fixedListImplementation => jsFixedArrayClass;
   ClassElement get growableListImplementation => jsExtendableArrayClass;
   ClassElement get mapImplementation => mapLiteralClass;
   ClassElement get constMapImplementation => constMapLiteralClass;
   ClassElement get functionImplementation => jsFunctionClass;
   ClassElement get typeImplementation => typeLiteralClass;
   ClassElement get boolImplementation => jsBoolClass;
   ClassElement get nullImplementation => jsNullClass;
 }