[filebrowser] Save sorting field/order for modal dialogs, show spinner when scanning directories.

chrome/browser/resources/file_manager/js/directory_model.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.
 
 // If directory files changes too often, don't rescan directory more than once
 // per specified interval
 const SIMULTANEOUS_RESCAN_INTERVAL = 1000;
 
 /**
  * Data model of the file manager.
@@ skipping 320 matching lines @@
    */
   scan_: function(callback) {
     if (this.rescanTimeout_) {
       clearTimeout(this.rescanTimeout_);
       this.rescanTimeout_ = 0;
     }
     if (this.runningScan_)
       this.runningScan_.cancel();
     this.pendingScan_ = null;
 
+    var onDone = function() {
+      cr.dispatchSimpleEvent(this, 'scan-completed');
+      callback();
+    }.bind(this);
+
     // Clear the table first.
     this.fileList_.splice(0, this.fileList_.length);
-    this.runningScan_ = this.createScanner_(this.fileList_, callback);
+    cr.dispatchSimpleEvent(this, 'scan-started');
+    this.runningScan_ = this.createScanner_(this.fileList_, onDone);
     this.runningScan_.run();
   },
 
   prefetchCacheForSorting_: function(entries, callback) {
     var field = this.fileList_.sortStatus.field;
     if (field) {
       this.prepareSortEntries_(entries, field, callback);
     } else {
       callback();
       return;
@@ skipping 524 matching lines @@
 
   recordMetrics_: function() {
     metrics.recordInterval('DirectoryScan');
     if (this.dir_.fullPath ==
         '/' + DirectoryModel.DOWNLOADS_DIRECTORY) {
       metrics.recordMediumCount("DownloadsCount", this.list_.length);
     }
   }
 };