Reify type params on map literals

test/codegen_expected/language/compile_time_constant_r_test_none_multi.js

 dart_library.library('language/compile_time_constant_r_test_none_multi', null, /* Imports */[
   'dart_sdk'
 ], function load__compile_time_constant_r_test_none_multi(exports, dart_sdk) {
   'use strict';
   const core = dart_sdk.core;
   const dart = dart_sdk.dart;
   const dartx = dart_sdk.dartx;
   const compile_time_constant_r_test_none_multi = Object.create(null);
   let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
   compile_time_constant_r_test_none_multi.x = "x";
-  compile_time_constant_r_test_none_multi.y = dart.const(dart.map([0, "y"]));
+  compile_time_constant_r_test_none_multi.y = dart.const(dart.map([0, "y"], core.int, core.String));
   compile_time_constant_r_test_none_multi.main = function() {
     core.print(compile_time_constant_r_test_none_multi.x);
     core.print(compile_time_constant_r_test_none_multi.y);
     let z = 1 + 1 + 1;
     core.print(z);
   };
   dart.fn(compile_time_constant_r_test_none_multi.main, VoidTodynamic());
   // Exports:
   exports.compile_time_constant_r_test_none_multi = compile_time_constant_r_test_none_multi;
 });