Fix DOM Isolate affinity for interceptors

tests/compiler/dart2js_native/multiscript_part2_test.dart

+// Copyright (c) 2014, 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";
+
+// Methods on (shared) native classes should have DOM isolate affinity.
+// Test that part1 and part2 can be loaded into the same JavaScript context
+// without conflicts.
+
+class A native "AA" {
+  // [foo] is the same in both isolates but optimized differently.
+  foo(x) => x is String;
+
+  // [bar] has different definitions in the two isolates.
+  bar(x) => 'two:$x';
+}
+
+makeA() native;
+
+void setup() native """
+// Use existing definition if present to force sharing.
+if (typeof AA == "undefined") {
+  AA = function AA() {};
+}
+makeA = function(){return new AA;};
+""";
+
+main() {
+  setup();
+
+  Expect.equals(false, makeA().foo(123));
+  Expect.equals('two:hi', makeA().bar('hi'));
+}