Reflect scanning status in command UI. Only allow import once scanning is complete.

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}
- * @implements {importer.ScanResult}
  */
 function TestMediaScanner() {
+
+  /** @private {!importer.ScanResult} */
+  this.scans_ = [];
+
   /**
    * List of file entries found while scanning.
    * @type {!Array.<!FileEntry>}
    */
   this.fileEntries = [];
 
   /** @type {number} */
   this.totalBytes = 100;
 
   /** @type {number} */
   this.scanDuration = 100;
 
-  /** @type {!Promise.<!importer.ScanResult>} */
-  this.whenFinished;
+  /** @private {!Array.<!importer.ScanObserver>} */
+  this.observers = [];
 }
 
 /** @override */
+TestMediaScanner.prototype.addObserver = function(observer) {
+  this.observers.push(observer);
+};
+
+/** @override */
+TestMediaScanner.prototype.removeObserver = function(observer) {
+  var index = this.observers.indexOf(observer);
+  if (index > -1) {
+    this.observers.splice(index, 1);
+  } else {
+    console.warn('Ignoring request to remove observer that is not registered.');
+  }
+};
+
+/** @override */
 TestMediaScanner.prototype.scan = function(entries) {
-  var result = new TestScanResult(this);
-  this.whenFinished = Promise.resolve(result);
+  var result = new TestScanResult(this.fileEntries);
+  result.totalBytes = this.totalBytes;
+  result.scanDuration = this.scanDuration;
+  this.scans_.push(result);
   return result;
 };
 
 /**
+ * Finalizes all previously started scans.
+ */
+TestMediaScanner.prototype.finalizeScans = function() {
+  this.scans_.forEach(this.finalize.bind(this));
+};
+
+/**
+ * Notifies observers that a scan has finished.
+ * @param {!importer.ScanResult} result
+ */
+TestMediaScanner.prototype.finalize = function(result) {
+  result.finalize();
+  this.observers.forEach(
+      function(observer) {
+        observer(importer.ScanEvent.FINALIZED, result);
+      });
+};
+
+/**
+ * @param {number} expected
+ */
+TestMediaScanner.prototype.assertScanCount = function(expected) {
+  assertEquals(expected, this.scans_.length);
+};
+
+/**
  * importer.MediaScanner and importer.ScanResult test double.
  *
  * @constructor
  * @struct
- * @implements {importer.MediaScanner}
  * @implements {importer.ScanResult}
  *
- * @param {!TestMediaScanner} scanner
+ * @param {!Array.<!FileEntry>} fileEntries
  */
-function TestScanResult(scanner) {
-  /** @private {!TestMediaScanner} */
-  this.scanner_ = scanner;
+function TestScanResult(fileEntries) {
+  /**
+   * 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;
+
+  /** @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));
 }
 
 /** @override */
 TestScanResult.prototype.getFileEntries = function() {
-  return this.scanner_.fileEntries;
+  return this.fileEntries;
 };
 
 /** @override */
 TestScanResult.prototype.getTotalBytes = function() {
-  return this.scanner_.totalBytes;
+  return this.totalBytes;
 };
 
 /** @override */
 TestScanResult.prototype.getScanDurationMs = function() {
-  return this.scanner_.scanDuration;
+  return this.scanDuration;
 };
 
 /** @override */
-TestScanResult.prototype.whenFinished = function() {
-  return this.scanner_.whenFinished;
+TestScanResult.prototype.finalize = function() {
+  return this.resolveResult_(this);
 };
+
+/** @override */
+TestScanResult.prototype.whenFinal = function() {
+  return this.whenFinal_;
+};
+
+/** @override */
+TestScanResult.prototype.isFinal = function() {
+  return this.settled_;
+};