Revert "Native mixin interceptor bug fix"

tests/compiler/dart2js_native/native_mixin_multiple2_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";
-
-// Test that native classes can access methods defined only by mixins.
-
-class A native "A" {
-  foo(x, [y]) => '$x;$y';
-}
-
-class B extends A with M1, M2, M3 native "B" {
-}
-
-class M1 {}
-
-class M2 {
-  // These methods are only defined in this non-first, non-last mixin.
-  plain(x) => 'P $x';
-  bar(x, [y]) => '$y,$x';
-}
-
-class M3 {}
-
-makeB() native;
-
-void setup() native """
-function B() {}
-makeB = function(){return new B;};
-""";
-
-main() {
-  setup();
-
-  B b = makeB();
-  Expect.equals('1;2', b.foo(1,2));
-  Expect.equals('2;null', b.foo(2));
-  Expect.equals('P 3', b.plain(3));
-  Expect.equals('100,4', b.bar(4,100));
-  Expect.equals('null,5', b.bar(5));
-}