Chrome OS wallpaper manager.

chrome/browser/resources/chromeos/wallpaper_manager/manifest.json

 {
   // chrome-extension://obklkkbkpaoaejdabbfldmcfplpdgolj/
   "key": "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC6czTauf4/ISarT2JOcjcanIq+kcL/2UOF56QqXNT6PFgEwBG1i9Tfw/dTE59qWdGuxWt4yQlChewOFaRP3nb9AygPFXO31pNXaCY9xyDsjE5RhVvVB0GJa3VHFITIROpBSJHXNOqZBm706A8SFCTauasdWPFSE6Y7sA13t1P0MwIDAQAB",
   "name": "Wallpaper Picker",
   // Updates version to 0.2 for v2 version wallpaper picker. Otherwise the event
   // listener can not register appropriately. See crbug/157717.
   "version": "0.2",
   "manifest_version": 2,
   "description": "An experimental wallpaper picker UI",
   "icons": {
     "128": "images/icon128.png"
   },
   "permissions": [
     "alarms",
+    "app.window.alpha",
     "experimental",

[garykac1, 2014/08/13 17:21:29]

Previously, transparentBackground required 'experimental' permission, but now
that it has a separate permission you should no longer need it (unless you're
using another experimental feature).

     "storage",
     "unlimitedStorage",
     {"fileSystem": ["write"]},
     "wallpaperPrivate",
     "https://storage.googleapis.com/"
   ],
   "app": {
     "background": {
       "scripts": [
         "js/constants.js",
         "js/util.js",
         "js/event_page.js"
       ]
     }
   },
   "display_in_launcher": false
 }