Do not use the namer for naming closure elements.

tests/compiler/dart2js/js_backend_cps_ir_closures_test.dart

Index: tests/compiler/dart2js/js_backend_cps_ir_closures_test.dart
diff --git a/tests/compiler/dart2js/js_backend_cps_ir_closures_test.dart b/tests/compiler/dart2js/js_backend_cps_ir_closures_test.dart
index ddad2f6b53475ccb98c19872bee2126612712b7b..cc20b1b58ab44d4a2d117581ce646c6fbbe2eaad 100644
--- a/tests/compiler/dart2js/js_backend_cps_ir_closures_test.dart
+++ b/tests/compiler/dart2js/js_backend_cps_ir_closures_test.dart
@@ -21,12 +21,12 @@ main(x) {
 """,
 r"""
 function(x) {
-  var box_0, a;
-  box_0 = {};
-  box_0.x_0 = x;
-  a = new V.main_a(box_0);
-  x = box_0.x_0;
-  box_0.x_0 = J.getInterceptor$ns(x).$add(x, "1");
+  var _box_0, a;
+  _box_0 = {};
+  _box_0._captured_x_0 = x;
+  a = new V.main_a(_box_0);
+  x = _box_0._captured_x_0;
+  _box_0._captured_x_0 = J.getInterceptor$ns(x).$add(x, "1");
   P.print(a.call$0());
   return null;
 }"""),
@@ -55,12 +55,12 @@ main() {
 """,
 r"""
 function() {
-  var box_0, a, x;
-  box_0 = {};
-  box_0.x_0 = 122;
-  a = new V.main_closure(box_0);
-  x = box_0.x_0;
-  box_0.x_0 = J.getInterceptor$ns(x).$add(x, 1);
+  var _box_0, a, x;
+  _box_0 = {};
+  _box_0._captured_x_0 = 122;
+  a = new V.main_closure(_box_0);
+  x = _box_0._captured_x_0;
+  _box_0._captured_x_0 = J.getInterceptor$ns(x).$add(x, 1);
   P.print(a.call$0());
   return null;
 }"""),
@@ -78,12 +78,12 @@ main() {
 """,
 r"""
 function() {
-  var box_0, a, x;
-  box_0 = {};
-  box_0.x_0 = 122;
-  a = new V.main_closure(box_0);
-  x = box_0.x_0;
-  box_0.x_0 = J.getInterceptor$ns(x).$add(x, 1);
+  var _box_0, a, x;
+  _box_0 = {};
+  _box_0._captured_x_0 = 122;
+  a = new V.main_closure(_box_0);
+  x = _box_0._captured_x_0;
+  _box_0._captured_x_0 = J.getInterceptor$ns(x).$add(x, 1);
   P.print(a.call$0().call$0());
   return null;
 }"""),