Issue 4580 - Do not use Promise based storage API

lib/prefs.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 318 matching lines @@
     },
     enumerable: true
   });
 }
 
 function init()
 {
   let prefs = Object.keys(defaults);
   prefs.forEach(addPreference);
 
-  let localLoaded = browser.storage.local.get(prefs.map(prefToKey)).then(
+  let localLoaded = browser.storage.local.get(prefs.map(prefToKey),
     items =>
     {
       for (let key in items)
         overrides[keyToPref(key)] = items[key];
     }
   );
 
   let managedLoaded;
   if ("managed" in browser.storage)
   {
@@ skipping 32 matching lines @@
           eventEmitter.emit(pref);
         }
       }
     });
   }
 
   Prefs.untilLoaded = Promise.all([localLoaded, managedLoaded]).then(onLoaded);
 }
 
 init();