Fix unexpected error message when quickly select different wallpapers

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 be090ff18d4d8c9a55d477dd671deab3cad8a174..4f38bb311f834fdd228703447998bfd998cb3f64 100644
--- a/chrome/browser/resources/chromeos/wallpaper_manager/js/wallpaper_manager.js
+++ b/chrome/browser/resources/chromeos/wallpaper_manager/js/wallpaper_manager.js
@@ -507,13 +507,15 @@ function WallpaperManager(dialogDom) {
 
           var onSuccess = function(xhr) {
             var image = xhr.response;
-            chrome.wallpaperPrivate.setWallpaper(image, selectedItem.layout,
-                wallpaperURL,
-                self.onFinished_.bind(self, selectedGridItem, selectedItem));
-            self.currentWallpaper_ = wallpaperURL;
-            WallpaperUtil.saveWallpaperInfo(wallpaperURL, selectedItem.layout,
-                                            selectedItem.source);
-            self.wallpaperRequest_ = null;
+            if (image) {

[flackr, 2013/09/06 15:44:00]

onSuccess can actually be called if there's no response? Can you instead handle
this in fetchURL and avoid calling onSuccess if there's no response? Also,
shouldn't no response trigger the error handler?

+              chrome.wallpaperPrivate.setWallpaper(image, selectedItem.layout,
+                  wallpaperURL,
+                  self.onFinished_.bind(self, selectedGridItem, selectedItem));
+              self.currentWallpaper_ = wallpaperURL;
+              WallpaperUtil.saveWallpaperInfo(wallpaperURL, selectedItem.layout,
+                                              selectedItem.source);
+              self.wallpaperRequest_ = null;
+            }
           };
           var onFailure = function() {
             self.progressManager_.hideProgressBar(selectedGridItem);