Enable surprise me wallpaper for new profiles.

chrome/common/extensions/api/wallpaper_private.json

 // 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.
 
 [
   {
     "namespace":"wallpaperPrivate",
     "compiler_options": {
       "implemented_in": "chrome/browser/chromeos/extensions/wallpaper_private_api.h"
     },
@@ skipping 220 matching lines @@
             "parameters": [
               {
                 "type": "array",
                 "name": "results",
                 "items": {"type": "string"}
               }
             ]
           }
         ]
       }
+    ],
+    "events": [
+      {
+        "name": "onRequestEnableSurpriseMe",
+        "type": "function",
+        "description": "Fired to request enabling surprise me mode for new profiles.",
+        "parameters": []
+      }
     ]
   }
 ]