Make static tear-off closures a class, like instance tear-off closures.

tests/compiler/dart2js/static_closure_test.dart

Index: tests/compiler/dart2js/static_closure_test.dart
===================================================================
--- tests/compiler/dart2js/static_closure_test.dart	(revision 22664)
+++ tests/compiler/dart2js/static_closure_test.dart	(working copy)
@@ -17,5 +17,5 @@
 
   // If this test fail, please take a look at the use of
   // toStringWrapper in captureStackTrace in js_helper.dart.
-  Expect.isTrue(code.contains(r'print($.main);'));
+  Expect.isTrue(code.contains(r'print($.main$closure);'));
 }