Revert "Fix x.runtimeType for native classes"

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

Index: sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
index d1397c65c7d4362342cddf7913cfe67753ce9288..6dcad8db1106a21deb79de2dfaece4baf2e7f6e4 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
@@ -978,7 +978,6 @@ class JavaScriptBackend extends Backend {
           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);
@@ -1368,11 +1367,6 @@ class JavaScriptBackend extends Backend {
     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.
    *