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

tests/language/deferred_global_lib.dart

Index: tests/language/deferred_global_lib.dart
diff --git a/tests/language/deferred_global_lib.dart b/tests/language/deferred_global_lib.dart
index be4a001946758084f8df05bb4b2053a51f2a976e..a8fdca56326f77e60ffcc1f53940d6b179b2c364 100644
--- a/tests/language/deferred_global_lib.dart
+++ b/tests/language/deferred_global_lib.dart
@@ -11,6 +11,10 @@ final finalNonConstGlobal = (() {
 }());
 
 var lazyConstGlobal = "lazyConstGlobal";
+// Regression test for bug #21840.
+var const1Global = const {};
+final lazyConstGlobal2 = const1Global;
+
 var lazyNonConstGlobal = (() {
   sideEffectCounter++;
   return "lazyNonConstGlobal";