Native subclasses of a mixin include classes extending native classes

tests/compiler/dart2js_native/subclassing_4_test.dart

 // Copyright (c) 2013, 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.
 
 import "package:expect/expect.dart";
 import 'dart:_js_helper' show Creates, setNativeSubclassDispatchRecord;
 import 'dart:_interceptors' show Interceptor, findInterceptorForType;
 
-// Test calling convention of methods introduced on subclasses of native
-// class of mixin.
-
-doFoo(r, x) => '$x,${r.oof()},${r.miz()}';
+// Test calling convention on subclasses of native classes.
 
 class M {
   miz() => 'M';
 }
 
-class N native "N" {
-  foo(x) => (doFoo)(this, x);
-}
+class N native "N" {}
 
 class A extends N {}
 
 class B extends A with M {
-  // [oof] is introduced only on this subclass of a native class.  It should
-  // have interceptor calling convention.
-  oof() => 'B';
-  // [miz] is introduced only on the mixin-application A+M.
+  // The call to [miz] has a know type [B].  The call is in an intercepted
+  // method and to an intercepted method, so the ambient interceptor can be
+  // used.  For correct optimization of the interceptor, the compiler needs to
+  // (1) correctly determine that B is an intercepted type (because it extends a
+  // native class) and (2) realize that the intersection of [B] and subclasses
+  // of mixin applications of [M] is non-empty.
+  callMiz() => this.miz();
 }
 
 B makeB() native;
 
 @Creates('=Object')
 getBPrototype() native;
 
 void setup() native r"""
 function B() {}
 makeB = function(){return new B;};
-
 getBPrototype = function(){return B.prototype;};
 """;
 
 main() {
   setup();
 
   setNativeSubclassDispatchRecord(getBPrototype(), findInterceptorForType(B));
 
   B b = makeB();
-  Expect.equals('1,B,M', b.foo(1));
+  Expect.equals('M', b.callMiz());
 }