Reduce blinking of icons in the preview panel.

chrome/browser/resources/file_manager/js/file_manager.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.
 
 // Setting the src of an img to an empty string can crash the browser, so we
 // use an empty 1x1 gif instead.
 
 /**
  * FileManager constructor.
  *
@@ skipping 2231 matching lines @@
     };
 
     if (!selection.indexes.length) {
       this.updateCommonActionButtons_();
       this.updatePreviewPanelVisibility_();
       cr.dispatchSimpleEvent(this, 'selection-summarized');
       return;
     }
 
     this.previewSummary_.textContent = str('COMPUTING_SELECTION');
-    removeChildren(this.previewThumbnails_);
+    var thumbnails = this.document_.createDocumentFragment();
 
     var fileCount = 0;
     var byteCount = 0;
     var pendingFiles = [];
     var thumbnailCount = 0;
+    var thumbnailLoaded = -1;
+    var forcedShowTimeout = null;
+    var self = this;
+
+    function showThumbnails() {
+      if (forcedShowTimeout === null)
+        return;
+      clearTimeout(forcedShowTimeout);
+      forcedShowTimeout = null;
+
+      // Selection could change while images are loading.
+      if (self.selection == selection) {
+        removeChildren(self.previewThumbnails_);
+        self.previewThumbnails_.appendChild(thumbnails);
+      }
+    }
+
+    function onThumbnailLoaded() {
+      thumbnailLoaded++;
+      if (thumbnailLoaded == thumbnailCount)
+        showThumbnails();
+    }
 
     for (var i = 0; i < selection.indexes.length; i++) {
       var entry = this.directoryModel_.fileList.item(selection.indexes[i]);
       if (!entry)
         continue;
 
       selection.entries.push(entry);
       selection.urls.push(entry.toURL());
 
       if (selection.iconType == null) {
         selection.iconType = this.getIconType(entry);
       } else if (selection.iconType != 'unknown') {
         var iconType = this.getIconType(entry);
         if (selection.iconType != iconType)
           selection.iconType = 'unknown';
       }
 
       if (thumbnailCount < MAX_PREVIEW_THUMBAIL_COUNT) {
         var box = this.document_.createElement('div');
-        var imageLoadCalback = thumbnailCount == 0 &&
-                               this.initThumbnailZoom_.bind(this, box);
-        var thumbnail = this.renderThumbnailBox_(entry, true, imageLoadCalback);
+        function imageLoadCalback(index, box, img, transform) {
+          if (index == 0)
+            self.initThumbnailZoom_(box, img, transform);
+          onThumbnailLoaded();
+        }
+        var thumbnail = this.renderThumbnailBox_(entry, true,
+            imageLoadCalback.bind(null, thumbnailCount, box));
+        thumbnailCount++;
         box.appendChild(thumbnail);
         box.style.zIndex = MAX_PREVIEW_THUMBAIL_COUNT + 1 - i;
         box.addEventListener('click',
             this.dispatchDefaultTask_.bind(this, selection));
 
-        this.previewThumbnails_.appendChild(box);
-        thumbnailCount++;
+        thumbnails.appendChild(box);
       }
 
       selection.totalCount++;
 
       if (entry.isFile) {
         selection.fileCount += 1;
         if (!('cachedSize_' in entry)) {
           // Any file that hasn't been rendered may be missing its cachedSize_
           // property.  For example, visit a large file list, and press ctrl-a
           // to select all.  In this case, we need to asynchronously get the
           // sizes for these files before telling the world the selection has
           // been summarized.  See the 'computeNextFile' logic below.
           pendingFiles.push(entry);
         } else {
           selection.bytes += entry.cachedSize_;
           selection.showBytes |= this.getFileType(entry).type != 'hosted';
         }
       } else {
         selection.directoryCount += 1;
       }
     }
 
     // Now this.selection is complete. Update buttons.
     this.updateCommonActionButtons_();
     this.updatePreviewPanelVisibility_();
-
-    var self = this;
+    forcedShowTimeout = setTimeout(showThumbnails, 100);
+    onThumbnailLoaded();
 
     function cacheNextFile(fileEntry) {
       if (fileEntry) {
         // We're careful to modify the 'selection', rather than 'self.selection'
         // here, just in case the selection has changed since this summarization
         // began.
         selection.bytes += fileEntry.cachedSize_;
         selection.showBytes |= self.getFileType(fileEntry).type != 'hosted';
       }
 
@@ skipping 2098 matching lines @@
 
     chrome.fileBrowserPrivate.setGDataPreferences(changeInfo);
 
     if (oldValue) {
       event.target.removeAttribute('checked');
     } else {
       event.target.setAttribute('checked', 'checked');
     }
   };
 })();