Dart2js, move deferred global vars to the right output unit.

tests/language/deferred_global_lib.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.
 
 var sideEffectCounter = 0;
 
 final finalConstGlobal = "finalConstGlobal";
 final finalNonConstGlobal = (() {
   sideEffectCounter++;
   return "finalNonConstGlobal";
 }());
 
 var lazyConstGlobal = "lazyConstGlobal";
+// Regression test for bug #21840.
+var const1Global = const {};
+final lazyConstGlobal2 = const1Global;
+
 var lazyNonConstGlobal = (() {
   sideEffectCounter++;
   return "lazyNonConstGlobal";
 }());
 
 readFinalConstGlobal() => finalConstGlobal;
 readFinalNonConstGlobal() => finalNonConstGlobal;
 readLazyConstGlobal() => lazyConstGlobal;
 readLazyNonConstGlobal() => lazyNonConstGlobal;
 writeLazyConstGlobal(x) { lazyConstGlobal = x; }
 writeLazyNonConstGlobal(x) { lazyNonConstGlobal = x; }