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

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

 // Copyright (c) 2013 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.
 
 var WALLPAPER_PICKER_WIDTH = 574;
 var WALLPAPER_PICKER_HEIGHT = 420;
 
 var wallpaperPickerWindow;
 
 var surpriseWallpaper = null;
@@ skipping 97 matching lines @@
 };
 
 /**
  * Sets a new random wallpaper if one has not already been set today.
  * @private
  */
 SurpriseWallpaper.prototype.updateRandomWallpaper_ = function() {
   var self = this;
   Constants.WallpaperSyncStorage.get(
       Constants.AccessLastSurpriseWallpaperChangedDate, function(items) {
-    var dateString = new Date().toDateString();
-    // At most one random wallpaper per day.
-    if (items[Constants.AccessLastSurpriseWallpaperChangedDate] != dateString) {
-      self.setRandomWallpaper_(dateString);
-    }
+    var today = new Date().toDateString();
+    self.setRandomWallpaper_(today);
   });
 };
 
 /**
  * Sets wallpaper to one of the wallpapers displayed in wallpaper picker. If
  * the wallpaper download fails, retry one hour later. Wallpapers that are
  * disabled for surprise me are excluded.
  * @param {string} dateString String representation of current local date.
  * @private
  */
@@ skipping 10 matching lines @@
             element.available_for_surprise_me == undefined;
       });
       var index = Math.floor(Math.random() * filtered.length);
       var wallpaper = filtered[index];
       var wallpaperURL = wallpaper.base_url + Constants.HighResolutionSuffix;
       var onSuccess = function() {
         WallpaperUtil.saveToStorage(
             Constants.AccessLastSurpriseWallpaperChangedDate,
             dateString,
             true);
+        WallpaperUtil.saveWallpaperInfo(wallpaperURL, wallpaper.default_layout,
+          Constants.WallpaperSourceEnum.Online);

[bshe, 2015/03/04 19:45:39]

nit: 4 spaces indention for new line.

[xdai1, 2015/03/04 21:32:39]

Done.

       };
       WallpaperUtil.setOnlineWallpaper(wallpaperURL, wallpaper.default_layout,
           onSuccess, self.retryLater_.bind(self));
     }
   });
 };
 
 /**
  * Sets wallpaper to the wallpaper specified by item from rss. If downloading
  * the wallpaper fails, retry one hour later.
@@ skipping 24 matching lines @@
  * Disables the wallpaper surprise me feature. Clear all alarms and states.
  */
 SurpriseWallpaper.prototype.disable = function() {
   chrome.alarms.clearAll();
   // Makes last changed date invalid.
   WallpaperUtil.saveToStorage(Constants.AccessLastSurpriseWallpaperChangedDate,
                               '', true);
 };
 
 /**
- * Changes current wallpaper and sets up an alarm to schedule next change around
- * midnight.
+ * Changes current wallpaper once a day and sets up an alarm to schedule next
+ * change around midnight. If the surprise wallpaper was already set toady,
+ * then don't change it any more.
  */
 SurpriseWallpaper.prototype.next = function() {
   var nextUpdate = this.nextUpdateTime(new Date());
   chrome.alarms.create({when: nextUpdate});
-  this.tryChangeWallpaper();
+
+  var self = this;
+  Constants.WallpaperSyncStorage.get(

[bshe, 2015/03/04 19:45:39]

why do you want to move the check to here? Looks like we skipped checking from
wallpaper from rss this way, I worry it might cause problem.

[xdai1, 2015/03/04 21:32:39]

Since when surprise me is enabled, we only change wallpaper once a day (no
matter it's rss special wallpaper or a random surprise wallpaper). So it won't
miss rss wallpaper here. Both way will do the same thing. But I think it might
be more clear to put the check here?

[bshe, 2015/03/05 14:53:19]

Rss wallpaper is not saved to sync storage and we prefer to use the rss
wallpaper over random online wallpaper. Set rss wallpaper might not be success
on Chromebook on first try. We dont want to block the second try (1 hour later,
see retryLater_ function) in this case. If there is no bug that you are trying
to fix with this move, I would prefer to keep the check in the old place.

+    Constants.AccessLastSurpriseWallpaperChangedDate, function(items) {
+      var today = new Date().toDateString();
+      if (items[Constants.AccessLastSurpriseWallpaperChangedDate] != today) {
+        self.tryChangeWallpaper();
+    }
+  });
 };
 
 /**
  * Calculates when the next wallpaper change should be triggered.
  * @param {Date} now Current time.
  * @return {number} The time when next wallpaper change should happen.
  */
 SurpriseWallpaper.prototype.nextUpdateTime = function(now) {
   var nextUpdate = new Date(now.setDate(now.getDate() + 1)).toDateString();
   return new Date(nextUpdate).getTime();
@@ skipping 56 matching lines @@
     WallpaperUtil.requestSyncFS(function() {});
     if (changes[Constants.AccessSurpriseMeEnabledKey]) {
       if (changes[Constants.AccessSurpriseMeEnabledKey].newValue) {
         SurpriseWallpaper.getInstance().next();
       } else {
         SurpriseWallpaper.getInstance().disable();
       }
     }
 
     if (changes[Constants.AccessSyncWallpaperInfoKey]) {
-      var newValue = changes[Constants.AccessSyncWallpaperInfoKey].newValue;
-      Constants.WallpaperLocalStorage.get(Constants.AccessLocalWallpaperInfoKey,
-                                          function(items) {
-        // Normally, the wallpaper info saved in local storage and sync storage
-        // are the same. If the synced value changed by sync service, they may
-        // different. In that case, change wallpaper to the one saved in sync
-        // storage and update the local value.
-        var localValue = items[Constants.AccessLocalWallpaperInfoKey];
-        if (localValue == undefined ||
-            localValue.url != newValue.url ||
-            localValue.layout != newValue.layout ||
-            localValue.source != newValue.source) {
-          if (newValue.source == Constants.WallpaperSourceEnum.Online) {
-            // TODO(bshe): Consider schedule an alarm to set online wallpaper
-            // later when failed. Note that we need to cancel the retry if user
-            // set another wallpaper before retry alarm invoked.
-            WallpaperUtil.setOnlineWallpaper(newValue.url, newValue.layout,
-              function() {}, function() {});
-          } else if (newValue.source == Constants.WallpaperSourceEnum.Custom) {
-            WallpaperUtil.setCustomWallpaperFromSyncFS(newValue.url,
-                                                       newValue.layout);
-          } else if (newValue.source == Constants.WallpaperSourceEnum.Default) {
-            chrome.wallpaperPrivate.resetWallpaper();
+      var syncInfo = changes[Constants.AccessSyncWallpaperInfoKey].newValue;
+
+      Constants.WallpaperSyncStorage.get(Constants.AccessSurpriseMeEnabledKey,
+                                         function(enabledItems) {
+        var syncSurpriseMeEnabled =
+          enabledItems[Constants.AccessSurpriseMeEnabledKey];

[bshe, 2015/03/04 19:45:39]

nit: 4 spaces indention

[xdai1, 2015/03/04 21:32:39]

Done.

+
+        Constants.WallpaperSyncStorage.get(
+          Constants.AccessLastSurpriseWallpaperChangedDate, function(items) {

[bshe, 2015/03/04 19:45:39]

ditto

[xdai1, 2015/03/04 21:32:39]

Done.

+          var syncLastSurpriseMeChangedDate =

[bshe, 2015/03/04 19:45:39]

nit: function implementation should have 2 space indention.

[xdai1, 2015/03/04 21:32:39]

I think it already has 2 space indention?

+              items[Constants.AccessLastSurpriseWallpaperChangedDate];
+
+          var today = new Date().toDateString();
+          // If SurpriseMe is enabled and surprise wallpaper hasn't been changed
+          // today, we should not sync the change, instead onAlarm() will be
+          // triggered to update a surprise me wallpaper.
+          if (!syncSurpriseMeEnabled || (syncSurpriseMeEnabled &&
+                                syncLastSurpriseMeChangedDate == today)) {

[bshe, 2015/03/04 19:45:39]

nit: indention is off. Consider this:
if (!syncSurpriseMeEnabled ||
    (syncSurpriseMeEnabled && syncLastSurpriseMeChangedDate == today)) {
....
}

[xdai1, 2015/03/04 21:32:39]

Done.

+            Constants.WallpaperLocalStorage.get(
+              Constants.AccessLocalWallpaperInfoKey, function(infoItems) {
+                var localInfo =
+                  infoItems[Constants.AccessLocalWallpaperInfoKey];

[bshe, 2015/03/04 19:45:39]

nit: 4 space indention

[xdai1, 2015/03/04 21:32:39]

Done.

+                // Normally, the wallpaper info saved in local storage and sync
+                // storage are the same. If the synced value changed by sync
+                // service, they may different. In that case, change wallpaper
+                // to the one saved in sync storage and update the local value.
+                if (localInfo == undefined ||
+                    localInfo.url != syncInfo.url ||
+                    localInfo.layout != syncInfo.layout ||
+                    localInfo.source != syncInfo.source) {
+                  if (syncInfo.source == Constants.WallpaperSourceEnum.Online) {
+                    // TODO(bshe): Consider schedule an alarm to set online
+                    // wallpaper later when failed. Note that we need to cancel
+                    // the retry if user set another wallpaper before retry
+                    // alarm invoked.
+                    WallpaperUtil.setOnlineWallpaper(syncInfo.url,
+                        syncInfo.layout, function() {}, function() {});
+                  } else if (syncInfo.source ==
+                    Constants.WallpaperSourceEnum.Custom) {
+                      WallpaperUtil.setCustomWallpaperFromSyncFS(syncInfo.url,
+                          syncInfo.layout);
+                  } else if (syncInfo.source ==
+                              Constants.WallpaperSourceEnum.Default) {
+                      chrome.wallpaperPrivate.resetWallpaper();
+                  }
+                  WallpaperUtil.saveToStorage(
+                        Constants.AccessLocalWallpaperInfoKey, syncInfo, false);
+                }
+            });
           }
-          WallpaperUtil.saveToStorage(Constants.AccessLocalWallpaperInfoKey,
-                                      newValue, false);
-        }
+        });
       });
     }
   });
 });
 
 chrome.alarms.onAlarm.addListener(function() {
   SurpriseWallpaper.getInstance().next();
 });