Generate all runtime files from dart.

test/codegen/expect/varargs.js

 dart_library.library('varargs', null, /* Imports */[
-  "dart/_runtime"
+  'dart/_runtime'
 ], /* Lazy imports */[
 ], function(exports, dart) {
   'use strict';
   let dartx = dart.dartx;
   function varargsTest(x, ...others) {
     let args = [1, others];
     dart.dsend(x, 'call', ...args);
   }
   dart.fn(varargsTest);
   function varargsTest2(x, ...others) {
     let args = [1, others];
     dart.dsend(x, 'call', ...args);
   }
   dart.fn(varargsTest2);
   // Exports:
   exports.varargsTest = varargsTest;
   exports.varargsTest2 = varargsTest2;
 });