enable top-level @JS() getters

test/codegen/expect/cascade.js

 dart_library.library('cascade', null, /* Imports */[
   'dart_sdk'
 ], function(exports, dart_sdk) {
   'use strict';
   const core = dart_sdk.core;
   const dart = dart_sdk.dart;
   const dartx = dart_sdk.dartx;
   const cascade = Object.create(null);
   cascade.A = class A extends core.Object {
     A() {
       this.x = null;
     }
   };
   cascade.test_closure_with_mutate = function() {
     let a = new cascade.A();
     a.x = dart.fn(() => {
       core.print("hi");
       a = null;
     });
     let _ = a;
-    dart.dcall(_.x);
-    dart.dcall(_.x);
+    dart.dsend(_, 'x');
+    dart.dsend(_, 'x');
     core.print(a);
   };
   dart.fn(cascade.test_closure_with_mutate, dart.void, []);
   cascade.test_closure_without_mutate = function() {
     let a = new cascade.A();
     a.x = dart.fn(() => {
       core.print(a);
     });
-    dart.dcall(a.x);
-    dart.dcall(a.x);
+    dart.dsend(a, 'x');
+    dart.dsend(a, 'x');
     core.print(a);
   };
   dart.fn(cascade.test_closure_without_mutate, dart.void, []);
   cascade.test_mutate_inside_cascade = function() {
     let a = null;
     let _ = new cascade.A();
     _.x = a = null;
     _.x = a = null;
     a = _;
     core.print(a);
@@ skipping 63 matching lines @@
       this.x[dartx.add](3);
       this.x[dartx.add](4);
     }
   };
   dart.setSignature(cascade.Foo, {
     methods: () => ({test_final_field_generic: [dart.void, [dart.dynamic]]})
   });
   // Exports:
   exports.cascade = cascade;
 });