dart2js cps: Use oneshot interceptors and 'instanceof' expressions.

tests/compiler/dart2js/js_backend_cps_ir_closures_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.
 
 // Tests of closures.
 
 library closures_test;
 
 import 'js_backend_cps_ir.dart';
 
 const List<TestEntry> tests = const [
   const TestEntry("""
 main(x) {
   a() {
     return x;
   }
   x = x + '1';
   print(a());
 }
 """,
 r"""
 function(x) {
-  P.print(J.getInterceptor$ns(x).$add(x, "1"));
+  P.print(J.$add$ns(x, "1"));
 }"""),
 
   const TestEntry("""
 main(x) {
   a() {
     return x;
   }
   x = x + '1';
   print(a());
   return a;
 }
 """,
 r"""
 function(x) {
   var _box_0 = {}, a = new V.main_a(_box_0);
   _box_0.x = x;
-  _box_0.x = J.getInterceptor$ns(x = _box_0.x).$add(x, "1");
+  _box_0.x = J.$add$ns(_box_0.x, "1");
   P.print(a.call$0());
   return a;
 }"""),
 
   const TestEntry("""
 main(x) {
   a() {
     return x;
   }
   print(a());
@@ skipping 196 matching lines @@
 """,
 r"""
 function(x) {
   P.print(V.Foo$().get$getter().call$1(123));
 }"""),
 ];
 
 void main() {
   runTests(tests);
 }