Keep previous size in Directory 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,
@@ skipping 51 matching lines @@
 
     // Whether the size is the middle of loading.
     isSizeLoading: Boolean,
 
     /**
      * @private
      */
     hasFileSpecificInfo_: Boolean,
   },
 
-  // Clears fields.
-  clear: function() {
+  /**
+   * Clears fields.
+   * @param {boolean} keepSizeFields do not clear size and isSizeLoading fields.
+   */
+  clear: function(keepSizeFields) {
     this.type = '';
-    this.size = '';
     this.modiifcationTime = '';
     this.mediaMimeType = '';
     this.filePath = '';
 
     this.imageWidth = 0;
     this.imageHeight = 0;
     this.mediaTitle = '';
     this.mediaArtist = '';
     this.mediaAlbum = '';
     this.mediaDuration = 0;
     this.mediaGenre = '';
     this.mediaTrack = '';
     this.mediaYearRecorded = '';
     this.ifd = null;
 
-    this.isSizeLoading = false;
+    if (!keepSizeFields) {
+      this.size = '';
+      this.isSizeLoading = false;
+    }
   },
 
   /**
    * @param {string} type
    * @return {boolean}
    *
    * @private
    */
-  isImage_: function(type) { return type === 'image'; },
+  isImage_: function(type) {
+    return type === 'image';
+  },
 
   /**
    * @param {string} type
    * @return {boolean}
    *
    * @private
    */
-  isVideo_: function(type) { return type === 'video'; },
+  isVideo_: function(type) {
+    return type === 'video';
+  },
 
   /**
    * @param {string} type
    * @return {boolean}
    *
    * @private
    */
-  isAudio_: function(type) { return type === 'audio'; },
+  isAudio_: function(type) {
+    return type === 'audio';
+  },
 
   /**
    * Update private properties computed from metadata.
    * @private
    */
   metadataUpdated_: function() {
     this.hasFileSpecificInfo_ =
         !!(this.imageWidth && this.imageHeight || this.mediaTitle ||
            this.mediaArtist || this.mediaAlbum || this.mediaDuration ||
            this.mediaGenre || this.mediaTrack || this.mediaYearRecorded ||
@@ skipping 113 matching lines @@
 
     var result = '';
     for (var i = 0; i < values.length; i++) {
       if (values[i]) {
         result += (result ? ' ' : '') + values[i];
       }
     }
     return result;
   },
 });