Show a local folder's size in QuickView.

ui/file_manager/file_manager/foreground/elements/files_metadata_box.js

 // Copyright 2016 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.
 
 var FilesMetadataBox = Polymer({
   is: 'files-metadata-box',
 
   properties: {
     // File media type, e.g. image, video.
     type: String,
     size: String,
     modiifcationTime: String,
     filePath: String,
     mediaMimeType: String,
 
     // File type specific metadata below.
     imageWidth: Number,
     imageHeight: Number,
     mediaTitle: String,
     mediaArtist: String,
+
+    // Whether the value is the middle of loading.
+    loading: Boolean,

[fukino, 2016/09/06 09:12:44]

'loading' sounds like all the properties are loading.
How about using 'laodingSize' or 'isSizeLoading'?

[harukam, 2016/09/06 11:25:24]

Agree. I like 'isSizeLoading' better.

   },
 
   // Clears fields.
   clear: function() {
     this.type = '';
     this.size = '';
     this.modiifcationTime = '';
     this.mediaMimeType = '';
     this.filePath = '';
 
     this.imageWidth = 0;
     this.imageHeight = 0;
     this.mediaTitle = '';
     this.mediaArtist = '';
+
+    this.loading = false;
   },
 
   /**
    * @param {string} type
    * @return {boolean}
    *
    * @private
    */
   isImage_: function(type) { return type === 'image'; },
 
@@ skipping 34 matching lines @@
    * @return {string}
    *
    * @private
    */
   resolution_: function(imageWidth, imageHeight) {
     if (imageWidth && imageHeight)
       return imageWidth + " x " + imageHeight;
     return '';
   },
 
+  /**
+   * @param {boolean} loading
+   */
+  setLoading: function(loading) {

[fukino, 2016/09/06 09:12:44]

You can simply call, for example, 'metadataBox_.loading = true' 

[harukam, 2016/09/06 11:25:24]

Acknowledged.

+    this.loading = loading;
+  },
 });