dart2js: Use an abstract Name class for names in the generated JavaScript ast.

tests/compiler/dart2js/static_closure_test.dart

Index: tests/compiler/dart2js/static_closure_test.dart
diff --git a/tests/compiler/dart2js/static_closure_test.dart b/tests/compiler/dart2js/static_closure_test.dart
index 9581ac9b78b73af4800a7436125aca4265e1dc9a..5bf9171cf4ad0823ef06e60e0bbc1242ff460979 100644
--- a/tests/compiler/dart2js/static_closure_test.dart
+++ b/tests/compiler/dart2js/static_closure_test.dart
@@ -18,6 +18,6 @@ main() {
     // If this test fail, please take a look at the use of
     // toStringWrapper in captureStackTrace in js_helper.dart.
     Expect.isTrue(code.contains(
-        new RegExp(r'print\([$A-Z]+\.main\$closure\(\)\);')), code);
+        new RegExp(r'print\([$A-Z]+\.lib___main\$closure\(\)\);')), code);
   }));
 }