Show custom wallpaper container and cannot access wallpaper message when device offline.

chrome/browser/resources/chromeos/wallpaper_manager/js/wallpaper_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.
 
 /**
  * WallpaperManager constructor.
  *
  * WallpaperManager objects encapsulate the functionality of the wallpaper
  * manager extension.
  *
@@ skipping 66 matching lines @@
     }
   };
 
   /**
    * Requests wallpaper manifest file from server.
    */
   WallpaperManager.prototype.fetchManifest_ = function() {
     var xhr = new XMLHttpRequest();
     var locale = navigator.language;
     xhr.open('GET', ManifestBaseURL + locale + '.json', false);
-    xhr.send(null);
-    // TODO(bshe): We should save the downloaded manifest to local disk. Other
-    // components may want to use it (i.e. screen saver).
-    if (xhr.status === 200) {
-      this.parseManifest_(xhr.responseText);
-    } else {
-      // Fall back to en locale if current locale is not supported.
-      xhr.open('GET', ManifestBaseURL + 'en.json', false);
+    try {
       xhr.send(null);
+      // TODO(bshe): We should save the downloaded manifest to local disk. Other
+      // components may want to use it (i.e. screen saver).
       if (xhr.status === 200) {
         this.parseManifest_(xhr.responseText);
       } else {
-        this.manifest_ = {};
-        this.butterBar_.showError_(str('connectionFailed'));
+        // Fall back to en locale if current locale is not supported.
+        xhr.open('GET', ManifestBaseURL + 'en.json', false);
+        xhr.send(null);
+        if (xhr.status === 200) {
+          this.parseManifest_(xhr.responseText);

[flackr, 2012/10/16 15:29:48]

This nested structure which does the same thing to fallback duplicates all of
the logic. Can you make this use a list and try the first item, then fallback to
the next, etc.

[bshe, 2012/10/16 16:01:48]

Done.

On 2012/10/16 15:29:48, flackr wrote:

+        } else {
+          this.manifest_ = {};
+          this.butterBar_.showError_(str('connectionFailed'));
+        }
       }
+    } catch (e) {
+      this.manifest_ = {};
+      this.butterBar_.showError_(str('connectionFailed'));
     }
 
     // TODO(bshe): Fall back to saved manifest if there is a problem fetching
     // manifest from server.
   };
 
   /**
    * One-time initialization of various DOM nodes.
    */
   WallpaperManager.prototype.initDom_ = function() {
@@ skipping 265 matching lines @@
             selectedItem = wallpaperInfo;
           }
         }
       }
       this.wallpaperGrid_.dataModel = wallpapersDataModel;
       this.wallpaperGrid_.selectedItem = selectedItem;
     }
   };
 
 })();