Convert wallpaper picker to v2 app

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.
  *
  * @constructor
  * @param {HTMLElement} dialogDom The DOM node containing the prototypical
  *     extension UI.
  */
 
 function WallpaperManager(dialogDom) {
   this.dialogDom_ = dialogDom;
   this.document_ = dialogDom.ownerDocument;
   this.selectedCategory = null;
   this.butterBar_ = new ButterBar(this.dialogDom_);
   this.customWallpaperData_ = null;
   this.currentWallpaper_ = null;
+  this.wallpaperRequest_ = null;
   this.fetchManifest_();
-  this.initDom_();
 }
 
 // Anonymous 'namespace'.
 // TODO(bshe): Get rid of anonymous namespace.
 (function() {
 
   /**
    * Base URL of the manifest file.
    */
   /** @const */ var ManifestBaseURL = 'https://commondatastorage.googleapis.' +
@@ skipping 41 matching lines @@
       this.manifest_ = {};
     }
   };
 
   /**
    * Requests wallpaper manifest file from server.
    */
   WallpaperManager.prototype.fetchManifest_ = function() {
     var xhr = new XMLHttpRequest();
     var locale = navigator.language;
-    var urls = [
-        ManifestBaseURL + locale + '.json',
-        // Fallback url. Use 'en' locale by default.
-        ManifestBaseURL + 'en.json'];
-
-    for (var i = 0; i < urls.length; i++) {
-      xhr.open('GET', urls[i], false);
-      try {
-        xhr.send(null);
+    xhr.open('GET', ManifestBaseURL + locale + '.json', true);
+    var self = this;
+    try {
+      xhr.send(null);
+      xhr.addEventListener('load', function(e) {
         // TODO(bshe): We should save the downloaded manifest to local disk.
         // Other components may want to use it (i.e. screen saver).

[miket_OOO, 2012/11/12 21:39:46]

e.g., not i.e.

[bshe, 2012/11/12 22:24:28]

Done.

         if (xhr.status === 200) {
-          this.parseManifest_(xhr.responseText);
-          return;
+          self.parseManifest_(xhr.responseText);
+          self.initDom_();
+        } else {
+          // Fall back to en locale if current locale is not supported.
+          var xhrFallBack = new XMLHttpRequest();
+          xhrFallBack.open('GET', ManifestBaseURL + 'en.json', true);
+          try {
+            xhrFallBack.send(null);
+            xhrFallBack.addEventListener('load', function(e) {
+              if (xhrFallBack.status === 200) {
+                self.parseManifest_(xhrFallBack.responseText);
+              } else {
+                self.manifest_ = {};
+                self.butterBar_.showError_(str('connectionFailed'));

[miket_OOO, 2012/11/12 21:39:46]

What does the cast do here?

[flackr, 2012/11/12 22:00:34]

str is a function which returns the localized string defined on line 51, not a
cast.

[bshe, 2012/11/12 22:24:28]

you mean str('..')? It gets the localized string for us.

On 2012/11/12 21:39:46, miket wrote:

+              }
+              self.initDom_();
+            });
+          } catch (e) {
+            this.manifest_ = {};
+            this.butterBar_.showError_(str('connectionFailed'));
+            self.initDom_();
+            return;

[flackr, 2012/11/12 22:00:34]

Is there a reason for unrolling the for loop into a nested block with very
similar logic?

[bshe, 2012/11/12 23:53:38]

We now use async xmlhttp request. I wrote a sync loop function for it. But it
looks like less readable. 

On 2012/11/12 22:00:34, flackr wrote:

[flackr, 2012/11/13 02:19:07]

Ah of course, this can still be done asynchronously with a list of fallback
URL's to avoid repeating the code.

[bshe, 2012/11/13 15:24:46]

Agree. I will keep it this way.

On 2012/11/13 02:19:07, flackr wrote:

+          }
         }
-      } catch (e) {
+      });
+    } catch (e) {
         this.manifest_ = {};
         this.butterBar_.showError_(str('connectionFailed'));
+        self.initDom_();
         return;
-      }
     }
-    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() {
     i18nTemplate.process(this.document_, loadTimeData);
@@ skipping 283 matching lines @@
             selectedItem = wallpaperInfo;
           }
         }
       }
       this.wallpaperGrid_.dataModel = wallpapersDataModel;
       this.wallpaperGrid_.selectedItem = selectedItem;
     }
   };
 
 })();