Revert "Fix x.runtimeType for native classes"

sdk/lib/_internal/compiler/implementation/resolution/members.dart

Index: sdk/lib/_internal/compiler/implementation/resolution/members.dart
diff --git a/sdk/lib/_internal/compiler/implementation/resolution/members.dart b/sdk/lib/_internal/compiler/implementation/resolution/members.dart
index feda1c974639e69f1e632fcebfc820b4de601138..46d678dca016129d6212158b20fba1f2a1ca20f8 100644
--- a/sdk/lib/_internal/compiler/implementation/resolution/members.dart
+++ b/sdk/lib/_internal/compiler/implementation/resolution/members.dart
@@ -3207,22 +3207,17 @@ class ClassResolverVisitor extends TypeDefinitionVisitor {
         element.supertype = resolveSupertype(element, node.superclass);
       }
     }
-    // If the super type isn't specified, we provide a default.  The language
-    // specifies [Object] but the backend can pick a specific 'implementation'
-    // of Object - the JavaScript backend chooses between Object and
-    // Interceptor.
-    if (element.supertype == null) {
-      ClassElement superElement = compiler.backend.defaultSuperclass(element);
-      // Avoid making the superclass (usually Object) extend itself.
-      if (element != superElement) {
-        if (superElement == null) {
-          compiler.internalError("Internal error: cannot resolve Object",
-              node: node);
-        } else {
-          superElement.ensureResolved(compiler);
-        }
-        element.supertype = superElement.computeType(compiler);
+
+    // If the super type isn't specified, we make it Object.
+    final objectElement = compiler.objectClass;
+    if (!identical(element, objectElement) && element.supertype == null) {
+      if (objectElement == null) {
+        compiler.internalError("Internal error: cannot resolve Object",
+                               node: node);
+      } else {
+        objectElement.ensureResolved(compiler);
       }
+      element.supertype = objectElement.computeType(compiler);
     }
 
     assert(element.interfaces == null);