Reify type params on map literals

test/codegen_expected/language/lazy_map_test.js

 dart_library.library('language/lazy_map_test', null, /* Imports */[
   'dart_sdk',
   'expect'
 ], function load__lazy_map_test(exports, dart_sdk, expect) {
   'use strict';
   const core = dart_sdk.core;
   const dart = dart_sdk.dart;
   const dartx = dart_sdk.dartx;
   const expect$ = expect.expect;
   const lazy_map_test = Object.create(null);
   let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
   dart.defineLazy(lazy_map_test, {
     get data() {
-      return dart.map({a: 'a'});
+      return dart.map({a: 'a'}, core.String, core.String);
     },
     set data(_) {}
   });
   lazy_map_test.main = function() {
     expect$.Expect.equals('a', lazy_map_test.data[dartx.get]('a'));
   };
   dart.fn(lazy_map_test.main, VoidTodynamic());
   // Exports:
   exports.lazy_map_test = lazy_map_test;
 });