Fixes from polymer.dart API review

pkg/polymer/lib/src/job.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-library polymer.job;
-
-import 'dart:async' show Timer;
+part of polymer;
 
 /**
  * Invoke [callback] in [wait], unless the job is re-registered,
  * which resets the timer. For example:
  *
  *     _myJob = runJob(_myJob, callback, const Duration(milliseconds: 100));
  *
  * Returns a job handle which can be used to re-register a job.
  */
 // Dart note: renamed to runJob to avoid conflict with instance member "job".
-Job runJob(Job job, void callback(), Duration wait) {
+_Job _runJob(_Job job, void callback(), Duration wait) {
   if (job != null) {
     job.stop();
   } else {
-    job = new Job();
+    job = new _Job();
   }
   job.go(callback, wait);
   return job;
 }
 
-// TODO(jmesserly): it isn't clear to me what is supposed to be public API here.
-// Or what name we should use. "Job" is awfully generic.
-// (The type itself is not exported in Polymer.)
-// Remove this type in favor of Timer?
-class Job {
+// Public in Polymer.js but private as not sure it's the correct API for Dart.
+// Switch to Timer when 14414 is addressed.
+class _Job {
   Function _callback;
   Timer _timer;
 
   void go(void callback(), Duration wait) {
     this._callback = callback;
     _timer = new Timer(wait, complete);
   }
 
   void stop() {
     if (_timer != null) {
       _timer.cancel();
       _timer = null;
     }
   }
 
   void complete() {
     if (_timer != null) {
       stop();
       _callback();
     }
   }
 }