Decrease the lag when switching between different categories in the Cros wallpaper selector.

chrome/browser/resources/chromeos/wallpaper_manager/js/wallpaper_manager.js

Index: chrome/browser/resources/chromeos/wallpaper_manager/js/wallpaper_manager.js
diff --git a/chrome/browser/resources/chromeos/wallpaper_manager/js/wallpaper_manager.js b/chrome/browser/resources/chromeos/wallpaper_manager/js/wallpaper_manager.js
index 5d638ecbc448f4446ec4fd6cd1d751026ef33548..e0ebf271d90e4bf869f3da7e4e0319f5b105c959 100644
--- a/chrome/browser/resources/chromeos/wallpaper_manager/js/wallpaper_manager.js
+++ b/chrome/browser/resources/chromeos/wallpaper_manager/js/wallpaper_manager.js
@@ -455,7 +455,6 @@ function WallpaperManager(dialogDom) {
   WallpaperManager.prototype.initThumbnailsGrid_ = function() {
     this.wallpaperGrid_ = $('wallpaper-grid');
     wallpapers.WallpaperThumbnailsGrid.decorate(this.wallpaperGrid_);
-    this.wallpaperGrid_.autoExpands = true;
 
     this.wallpaperGrid_.addEventListener('change', this.onChange_.bind(this));
     this.wallpaperGrid_.addEventListener('dblclick', this.onClose_.bind(this));
@@ -1003,10 +1002,12 @@ function WallpaperManager(dialogDom) {
       };
 
       var self = this;
+      var numOnlineWallpaper = this.manifest_.wallpaper_list.length;
       var processResults = function(entries) {
         for (var i = 0; i < entries.length; i++) {
           var entry = entries[i];
           var wallpaperInfo = {
+                wallpaperId: numOnlineWallpaper + i,
                 baseURL: entry.name,
                 // The layout will be replaced by the actual value saved in
                 // local storage when requested later. Layout is not important
@@ -1021,6 +1022,7 @@ function WallpaperManager(dialogDom) {
         }
         if (loadTimeData.getBoolean('isOEMDefaultWallpaper')) {
           var oemDefaultWallpaperElement = {
+              wallpaperId: numOnlineWallpaper + entries.length,
               baseURL: 'OemDefaultWallpaper',
               layout: 'CENTER_CROPPED',
               source: Constants.WallpaperSourceEnum.OEM,
@@ -1067,11 +1069,13 @@ function WallpaperManager(dialogDom) {
                                        success, errorHandler);
     } else {
       this.document_.body.removeAttribute('custom');
-      for (var key in this.manifest_.wallpaper_list) {
+      var numOnlineWallpaper = this.manifest_.wallpaper_list.length;
+      for (var key = 0; key < numOnlineWallpaper; key++) {

[bshe, 2015/03/23 21:40:31]

nit: perhaps rename "key" to "i"?

[xdai1, 2015/03/23 22:06:12]

Done.

         if (selectedIndex == AllCategoryIndex ||
             this.manifest_.wallpaper_list[key].categories.indexOf(
                 selectedIndex - OnlineCategoriesOffset) != -1) {
           var wallpaperInfo = {
+            wallpaperId: key,
             baseURL: this.manifest_.wallpaper_list[key].base_url,
             layout: this.manifest_.wallpaper_list[key].default_layout,
             source: Constants.WallpaperSourceEnum.Online,