Disable surprise me automatically if the current wallpaper was set by a third party application.

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 331 matching lines @@
           }
         });
       });
     }
   });
 });
 
 chrome.alarms.onAlarm.addListener(function() {
   SurpriseWallpaper.getInstance().next();
 });
+
+chrome.wallpaperPrivate.OnWallpaperChangedBy3rdParty.addListener(function() {
+  WallpaperUtil.saveToStorage(Constants.AccessSurpriseMeEnabledKey,
+                              false, true);
+  SurpriseWallpaper.getInstance().disable();
+});