Add thumbnailMetadataItem to GalleryItem.

ui/file_manager/gallery/js/mosaic_mode.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.
 
 /**
  * @param {!Element} container Content container.
  * @param {!ErrorBanner} errorBanner Error banner.
  * @param {!cr.ui.ArrayDataModel} dataModel Data model.
  * @param {!cr.ui.ListSelectionModel} selectionModel Selection model.
  * @param {!VolumeManager} volumeManager Volume manager.
@@ skipping 529 matching lines @@
 /**
  * Content change handler.
  *
  * @param {!Event} event Event.
  * @private
  */
 Mosaic.prototype.onContentChange_ = function(event) {
   if (!this.tiles_)
     return;
 
-  if (!event.metadata)
+  if (!event.thumbnailChanged)
     return; // Thumbnail unchanged, nothing to do.
 
   var index = this.dataModel_.indexOf(event.item);
   if (index !== this.selectionModel_.selectedIndex)
     console.error('Content changed for unselected item');
 
   this.layoutModel_.invalidateFromTile_(index);
   this.tiles_[index].init();
   this.tiles_[index].unload();
   this.tiles_[index].load(
@@ skipping 1486 matching lines @@
     this.imageLoaded_ = false;
     this.imageLoading_ = false;
   }
 };
 
 /**
  * Initializes the thumbnail in the tile. Does not load an image, but sets
  * target dimensions using metadata.
  */
 Mosaic.Tile.prototype.init = function() {
-  var metadata = this.getItem().getMetadata();
   this.markUnloaded();
   this.left_ = null;  // Mark as not laid out.
 
   // Set higher priority for the selected elements to load them first.
   var priority = this.getAttribute('selected') ? 2 : 3;
 
   // Use embedded thumbnails on Drive, since they have higher resolution.
   this.thumbnailLoader_ = new ThumbnailLoader(
       this.getItem().getEntry(),
       ThumbnailLoader.LoaderType.CANVAS,
-      metadata,
+      this.getItem().getThumbnailMetadataItem(),
       undefined,  // Media type.
       [
         ThumbnailLoader.LoadTarget.EXTERNAL_METADATA,
         ThumbnailLoader.LoadTarget.FILE_ENTRY
       ]);
 
   // If no hidpi embedded thumbnail available, then use the low resolution
   // for preloading.
   if (this.thumbnailLoader_.getLoadTarget() ===
       ThumbnailLoader.LoadTarget.FILE_ENTRY) {
     this.thumbnailPreloader_ = new ThumbnailLoader(
         this.getItem().getEntry(),
         ThumbnailLoader.LoaderType.CANVAS,
-        metadata,
+        this.getItem().getThumbnailMetadataItem(),
         undefined,  // Media type.
         [
           ThumbnailLoader.LoadTarget.CONTENT_METADATA
         ],
         // Preloaders have always higher priotity, so the preload images
         // are loaded as soon as possible.
         2);
     if (!this.thumbnailPreloader_.getLoadTarget())
       this.thumbnailPreloader_ = null;
   }
@@ skipping 217 matching lines @@
   return new ImageRect(this.left_ - this.container_.scrollLeft, this.top_,
       this.width_, this.height_).inflate(-margin, -margin);
 };
 
 /**
  * @return {number} X coordinate of the tile center.
  */
 Mosaic.Tile.prototype.getCenterX = function() {
   return this.left_ + Math.round(this.width_ / 2);
 };