Reuse FileTasks when entries are not changed.

ui/file_manager/file_manager/common/js/util.js

 // Copyright (c) 2012 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.
 
 /**
  * Namespace for utility functions.
  */
 var util = {};
 
 /**
@@ skipping 665 matching lines @@
  */
 util.isSameEntry = function(entry1, entry2) {
   if (!entry1 && !entry2)
     return true;
   if (!entry1 || !entry2)
     return false;
   return entry1.toURL() === entry2.toURL();
 };
 
 /**
+ * Compares two entry arrays.
+ * @param {Array<!Entry>} entries1 The entry array to be compared.
+ * @param {Array<!Entry>} entries2 The entry array to be compared.
+ * @return {boolean} True if the both arrays contain same files or directories
+ *     in the same order. Returns true if both arrays are null.
+ */
+util.isSameEntries = function(entries1, entries2) {
+  if (!entries1 && !entries2)
+    return true;
+  if (!entries1 || !entries2)
+    return false;
+  if (entries1.length !== entries2.length)
+    return false;
+  for (var i = 0; i < entries1.length; i++) {
+    if (!util.isSameEntry(entries1[i], entries2[i])) {
+      return false;
+    }
+  }
+  return true;
+};
+
+/**
  * Compares two file systems.
  * @param {FileSystem} fileSystem1 The file system to be compared.
  * @param {FileSystem} fileSystem2 The file system to be compared.
  * @return {boolean} True if the both file systems are equal. Also, returns true
  *     if both file systems are null.
  */
 util.isSameFileSystem = function(fileSystem1, fileSystem2) {
   if (!fileSystem1 && !fileSystem2)
     return true;
   if (!fileSystem1 || !fileSystem2)
@@ skipping 383 matching lines @@
  * @return {!Promise} A promise which can be rejected by timeout.
  */
 util.timeoutPromise = function(promise, ms, opt_message) {
   return Promise.race([
     promise,
     util.delay(ms).then(function() {
       throw new Error(opt_message || 'Operation timed out.');
     })
   ]);
 };