Use FileSystem API to store data in Opera

background.js

Index: background.js
===================================================================
--- a/background.js
+++ b/background.js
@@ -36,22 +36,21 @@ 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)
@@ -146,31 +145,35 @@ function refreshIconAndContextMenu(tab)
       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)
 {