Fix the issue that wallpaper changes twice when both "onChanged" and "onAlarm" are fired.

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

Index: chrome/browser/resources/chromeos/wallpaper_manager/js/util.js
diff --git a/chrome/browser/resources/chromeos/wallpaper_manager/js/util.js b/chrome/browser/resources/chromeos/wallpaper_manager/js/util.js
index 272fb2224869217f606fdcab88c9186bd51be5f4..0722977066d97e3cddd7cda23b66c2e5f4b5830c 100644
--- a/chrome/browser/resources/chromeos/wallpaper_manager/js/util.js
+++ b/chrome/browser/resources/chromeos/wallpaper_manager/js/util.js
@@ -306,9 +306,11 @@ WallpaperUtil.saveWallpaperInfo = function(url, layout, source) {
  * @param {function} onSuccess The success callback. It must be called with
  *     current XMLHttprequest object.
  * @param {function} onFailure The failure callback.
+ * @param {function} onNotFound The not found callback.
  * @param {XMLHttpRequest=} opt_xhr The XMLHttpRequest object.
  */
-WallpaperUtil.fetchURL = function(url, type, onSuccess, onFailure, opt_xhr) {
+WallpaperUtil.fetchURL = function(
+    url, type, onSuccess, onFailure, onNotFound, opt_xhr) {

[bshe, 2015/03/09 14:16:09]

I think it is probably better to handle onNotFound in onFailure. Not all callers
care about onNotFound case.

[xdai1, 2015/03/09 21:07:10]

Done.

   var xhr;
   if (opt_xhr)
     xhr = opt_xhr;
@@ -322,6 +324,9 @@ WallpaperUtil.fetchURL = function(url, type, onSuccess, onFailure, opt_xhr) {
     xhr.addEventListener('load', function(e) {
       if (this.status == 200) {
         onSuccess(this);
+      } else if (this.status == 404) {
+        if (onNotFound)
+          onNotFound();
       } else {
         onFailure();
       }