Use FileSystem API to store data in Opera

background.js

 /*
  * This file is part of Adblock Plus <http://adblockplus.org/>,
  * Copyright (C) 2006-2013 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 23 matching lines @@
 var Synchronizer = require("synchronizer").Synchronizer;
 var Utils = require("utils").Utils;
 var Notification = require("notification").Notification;
 
 // Some types cannot be distinguished
 RegExpFilter.typeMap.OBJECT_SUBREQUEST = RegExpFilter.typeMap.OBJECT;
 RegExpFilter.typeMap.MEDIA = RegExpFilter.typeMap.FONT = RegExpFilter.typeMap.OTHER;
 
 var isFirstRun = false;
 var seenDataCorruption = false;
-var importingOldData = false;
 require("filterNotifier").FilterNotifier.addListener(function(action)
 {
   if (action == "load")
   {
-    importOldData();
+    var importingOldData = importOldData();
 
     var addonVersion = require("info").addonVersion;
     var prevVersion = localStorage.currentVersion;
     if (prevVersion != addonVersion)
     {
       isFirstRun = !prevVersion;
       localStorage.currentVersion = addonVersion;
       if (!importingOldData)
         addSubscription(prevVersion);
     }
@@ skipping 84 matching lines @@
     // Set context menu status according to whether current tab has whitelisted domain
     if (excluded)
       chrome.contextMenus.removeAll();
     else
       showContextMenu();
 }
 
 /**
  * Old versions for Opera stored patterns.ini in the localStorage object, this
  * will import it into FilterStorage properly.
+ * @return {Boolean} true if data import is in progress
  */
 function importOldData()
 {
   if ("patterns.ini" in localStorage)
   {
-    importingOldData = true;
     FilterStorage.loadFromDisk(localStorage["patterns.ini"]);
 
     var remove = [];
     for (var key in localStorage)
       if (key.indexOf("patterns.ini") == 0 || key.indexOf("patterns-backup") == 0)
         remove.push(key);
     for (var i = 0; i < remove.length; i++)
       delete localStorage[remove[i]];
+
+    return true;
   }
+  else
+    return false;
 }
 
 /**
  * This function is called on an extension update. It will add the default
  * filter subscription if necessary.
  */
 function addSubscription(prevVersion)
 {
   // Make sure to remove "Recommended filters", no longer necessary
   var toRemove = "https://easylist-downloads.adblockplus.org/chrome_supplement.txt";
@@ skipping 279 matching lines @@
   tab.sendMessage({type: "clickhide-deactivate"});
   refreshIconAndContextMenu(tab);
 });
 
 setTimeout(function()
 {
   var notificationToShow = Notification.getNextToShow();
   if (notificationToShow)
     showNotification(notificationToShow);
 }, 3 * 60 * 1000);