Move test to dart2js_extra since it does not apply to VM.

tests/compiler/dart2js_extra/bailout8_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.
 
+// Test that the right exception for dart2js is thrown in the presence of
+// bailouts.
+
 import "package:expect/expect.dart";
 
 var a;
 var b;
 
 bar() {
   a = a == null ? 42 : new Object();
   a += b;
 }
 
 foo() {
   a = a == null ? new Object() : 42;
   a--;
 }
 
 main() {
   for (int i = 0; i < 10; i++) {
     a = null;
     Expect.throws(foo, (e) => e is NoSuchMethodError);
     a = null;
+    // dart2js throws [ArgumentError], VM throws [NoSuchMethodError].
     Expect.throws(bar, (e) => e is ArgumentError);
   }
 }