Extract ContentScanner from DirectoryContent.

chrome/browser/resources/file_manager/js/async_util.js

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 'use strict';
 
 /**
  * Namespace for async utility functions.
  */
 var AsyncUtil = {};
@@ skipping 35 matching lines @@
  * Added tasks will be executed sequentially in order they were added.
  *
  * @constructor
  */
 AsyncUtil.Queue = function() {
   this.running_ = false;
   this.closures_ = [];
 };
 
 /**
+ * @return {boolean} True when a task is running, otherwise false.
+ */
+AsyncUtil.Queue.prototype.isRunning = function() {
+  return this.running_;
+};
+
+/**
  * Enqueues a closure to be executed.
  * @param {function(function())} closure Closure with a completion callback to
  *     be executed.
  */
 AsyncUtil.Queue.prototype.run = function(closure) {
   this.closures_.push(closure);
   if (!this.running_)
     this.continue_();
 };
 
 /**
  * Serves the next closure from the queue.
  * @private
  */
 AsyncUtil.Queue.prototype.continue_ = function() {
   if (!this.closures_.length) {
     this.running_ = false;
     return;
   }
 
   // Run the next closure.
   this.running_ = true;
   var closure = this.closures_.shift();
   closure(this.continue_.bind(this));
 };
 
 /**
+ * Cancels all pending tasks. Note that this does NOT cancel the task running
+ * currently.
+ */
+AsyncUtil.Queue.prototype.cancel = function() {
+  this.closures_ = [];
+};
+
+/**
  * Creates a class for executing several asynchronous closures in a group in
  * a dependency order.
  *
  * @constructor
  */
 AsyncUtil.Group = function() {
   this.addedTasks_ = {};
   this.pendingTasks_ = {};
   this.finishedTasks_ = {};
   this.completionCallbacks_ = [];
@@ skipping 145 matching lines @@
 /**
  * Cancels all scheduled runs (if any).
  * @private
  */
 AsyncUtil.Aggregation.prototype.cancelScheduledRuns_ = function() {
   if (this.scheduledRunsTimer_) {
     clearTimeout(this.scheduledRunsTimer_);
     this.scheduledRunsTimer_ = null;
   }
 };