Fixes from polymer.dart API review

pkg/polymer/lib/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;
-
-/**
- * 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) {
-  if (job != null) {
-    job.stop();
-  } else {
-    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 {
-  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();
-    }
-  }
-}