Enable surprise me wallpaper for new profiles.

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 256 matching lines @@
         WallpaperUtil.saveToStorage(Constants.AccessLocalWallpaperInfoKey,
                                     newValue, false);
       }
     });
   }
 });
 
 chrome.alarms.onAlarm.addListener(function() {
   SurpriseWallpaper.getInstance().next();
 });
+
+/**
+ * Enables surprise me wallpaper iff it has not already been configured.
+ */
+chrome.wallpaperPrivate.onRequestEnableSurpriseMe.addListener(function() {
+  Constants.WallpaperSyncStorage.get(Constants.AccessSurpriseMeEnabledKey,
+                                      function(items) {
+    if (!items.hasOwnProperty(Constants.AccessSurpriseMeEnabledKey)) {

[Nikita (slow), 2014/04/08 16:58:27]

I wonder if that's the right time to check for this property since it may not
have been synced at this point.

[Harry McCleave, 2014/04/09 02:41:33]

My impression was that if this sync fails for whatever reason, a local copy of
the preferences will split off and when sync succeeds conflicts will be resolved
in the favor of the server values which would be the intended behaviour?

[bshe, 2014/04/09 14:32:15]

Is this going to be called when an existing user logged in on a new device? If
so, it might be safer to delay this operation for something like 1 hour or so
(or after sync is done if we can detect such event). Otherwise, we may change
the wallpaper of existing user first and then revert to the correct one. It may
confuse user.

On 2014/04/09 02:41:33, Harry McCleave wrote:

+      WallpaperUtil.saveToStorage(Constants.AccessSurpriseMeEnabledKey,
+                                  true, true);
+    }
+  });
+});