Cancel scans when directory changed.

ui/file_manager/file_manager/background/js/mock_media_scanner.js

 // Copyright 2014 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.
 
 /**
  * importer.MediaScanner and importer.ScanResult test double.
  *
  * @constructor
  * @struct
  * @implements {importer.MediaScanner}
@@ skipping 85 matching lines @@
 };
 
 /**
  * @param {number} expected
  */
 TestMediaScanner.prototype.assertScanCount = function(expected) {
   assertEquals(expected, this.scans_.length);
 };
 
 /**
+ * @param {number} expected

[mtomasz, 2015/04/01 02:28:45]

There is no "expected" in the argument list.

[Steve McKay, 2015/04/01 03:52:52]

Done.

+ */
+TestMediaScanner.prototype.assertLastScanCanceled = function() {
+  assertTrue(this.scans_.length > 0);
+  assertTrue(this.scans_[this.scans_.length - 1].canceled());
+};
+
+/**
  * importer.MediaScanner and importer.ScanResult test double.
  *
  * @constructor
  * @struct
  * @implements {importer.ScanResult}
  *
  * @param {!Array.<!FileEntry>} fileEntries
  */
 function TestScanResult(fileEntries) {
+
+  this.scanId_ = ++TestScanResult.lastId_;
   /**
    * List of file entries found while scanning.
    * @type {!Array.<!FileEntry>}
    */
   this.fileEntries = fileEntries.slice();
 
   /** @type {number} */
   this.totalBytes = 100;
 
   /** @type {number} */
   this.scanDuration = 100;
 
   /** @type {function} */
   this.resolveResult_;
 
   /** @type {function} */
   this.rejectResult_;
 
   /** @type {boolean} */
   this.settled_ = false;
 
+  /** @private {boolean} */
+  this.canceled_ = false;
+
   /** @type {!Promise.<!importer.ScanResult>} */
   this.whenFinal_ = new Promise(
       function(resolve, reject) {
         this.resolveResult_ = function(result) {
           this.settled_ = true;
           resolve(result);
         }.bind(this);
         this.rejectResult_ = function() {
           this.settled_ = true;
           reject();
         }.bind(this);
       }.bind(this));
 }
 
+/** @private {number} */
+TestScanResult.lastId_ = 0;
+
+/** @struct */
+TestScanResult.prototype = {
+  /** @return {string} */
+  get name() { return 'TestScanResult(' + this.scanId_ + ')' }
+};
+
 /** @override */
 TestScanResult.prototype.getFileEntries = function() {
   return this.fileEntries;
 };
 
 /** @override */
 TestScanResult.prototype.finalize = function() {
   return this.resolveResult_(this);
 };
 
 /** @override */
 TestScanResult.prototype.whenFinal = function() {
   return this.whenFinal_;
 };
 
 /** @override */
 TestScanResult.prototype.isFinal = function() {
   return this.settled_;
 };
 
 /** @override */
-TestScanResult.prototype.isInvalidated = function() {
-  return false;
+TestScanResult.prototype.cancel = function() {
+  this.canceled_ = true;
 };
 
 /** @override */
+TestScanResult.prototype.canceled = function() {
+  return this.canceled_;
+};
+
+/** @override */
 TestScanResult.prototype.getStatistics = function() {
   return {
     scanDuration: this.scanDuration,
     newFileCount: this.fileEntries.length,
     duplicates: {},
     sizeBytes: this.totalBytes
   };
 };
 
 /**
@@ skipping 11 matching lines @@
    * @public {boolean}
    */
   this.triggered = false;
 };
 
 /**
  * @override
  */
 TestDirectoryWatcher.prototype.addDirectory = function() {
 };