Index: lib/filterStorage.js
===================================================================
--- a/lib/filterStorage.js
+++ b/lib/filterStorage.js
@@ -75,37 +75,46 @@
 
   /**
    * Map of properties listed in the filter storage file before the sections
    * start. Right now this should be only the format version.
    */
   fileProperties: Object.create(null),
 
   /**
-   * List of filter subscriptions containing all filters
-   * @type {Subscription[]}
+   * Generator for filter subscriptions containing all filters
+   * @type {Subscription.Generator}
    */
-  subscriptions: [],
+  *subscriptions()
+  {
+    for (let subscription of this.knownSubscriptions.values())
+      yield subscription;
+  },
+
+  subscriptionCount()
+  {
+    return this.knownSubscriptions.size;
+  },
 
   /**
    * Map of subscriptions already on the list, by their URL/identifier
    * @type {Map.<string,Subscription>}
    */
   knownSubscriptions: new Map(),
 
   /**
    * Finds the filter group that a filter should be added to by default. Will
    * return null if this group doesn't exist yet.
    * @param {Filter} filter
    * @return {?SpecialSubscription}
    */
   getGroupForFilter(filter)
   {
     let generalSubscription = null;
-    for (let subscription of FilterStorage.subscriptions)
+    for (let subscription of FilterStorage.subscriptions())
     {
       if (subscription instanceof SpecialSubscription && !subscription.disabled)
       {
         // Always prefer specialized subscriptions
         if (subscription.isDefaultFor(filter))
           return subscription;
 
         // If this is a general subscription - store it as fallback
@@ -123,75 +132,38 @@
    * Adds a filter subscription to the list
    * @param {Subscription} subscription filter subscription to be added
    */
   addSubscription(subscription)
   {
     if (FilterStorage.knownSubscriptions.has(subscription.url))
       return;
 
-    FilterStorage.subscriptions.push(subscription);
     FilterStorage.knownSubscriptions.set(subscription.url, subscription);
     addSubscriptionFilters(subscription);
 
     filterNotifier.emit("subscription.added", subscription);
   },
 
   /**
    * Removes a filter subscription from the list
    * @param {Subscription} subscription filter subscription to be removed
    */
   removeSubscription(subscription)
   {
-    for (let i = 0; i < FilterStorage.subscriptions.length; i++)
-    {
-      if (FilterStorage.subscriptions[i].url == subscription.url)
-      {
-        removeSubscriptionFilters(subscription);
-
-        FilterStorage.subscriptions.splice(i--, 1);
-        FilterStorage.knownSubscriptions.delete(subscription.url);
-
-        // This should be the last remaining reference to the Subscription
-        // object.
-        Subscription.knownSubscriptions.delete(subscription.url);
-
-        filterNotifier.emit("subscription.removed", subscription);
-        return;
-      }
-    }
-  },
+    if (!FilterStorage.knownSubscriptions.has(subscription.url))
+      return;
+    removeSubscriptionFilters(subscription);
+    FilterStorage.knownSubscriptions.delete(subscription.url);
 
-  /**
-   * Moves a subscription in the list to a new position.
-   * @param {Subscription} subscription filter subscription to be moved
-   * @param {Subscription} [insertBefore] filter subscription to insert before
-   *        (if omitted the subscription will be put at the end of the list)
-   */
-  moveSubscription(subscription, insertBefore)
-  {
-    let currentPos = FilterStorage.subscriptions.indexOf(subscription);
-    if (currentPos < 0)
-      return;
+    // This should be the last remaining reference to the Subscription
+    // object.
+    Subscription.knownSubscriptions.delete(subscription.url);
 
-    let newPos = -1;
-    if (insertBefore)
-      newPos = FilterStorage.subscriptions.indexOf(insertBefore);
-
-    if (newPos < 0)
-      newPos = FilterStorage.subscriptions.length;
-
-    if (currentPos < newPos)
-      newPos--;
-    if (currentPos == newPos)
-      return;
-
-    FilterStorage.subscriptions.splice(currentPos, 1);
-    FilterStorage.subscriptions.splice(newPos, 0, subscription);
-    filterNotifier.emit("subscription.moved", subscription);
+    filterNotifier.emit("subscription.removed", subscription);
   },
 
   /**
    * Replaces the list of filters in a subscription by a new list
    * @param {Subscription} subscription filter subscription to be updated
    * @param {Filter[]} filters new filter list
    */
   updateSubscriptionFilters(subscription, filters)
@@ -368,17 +340,16 @@
       parser.process(line);
       if (line === null)
       {
         let knownSubscriptions = new Map();
         for (let subscription of parser.subscriptions)
           knownSubscriptions.set(subscription.url, subscription);
 
         this.fileProperties = parser.fileProperties;
-        this.subscriptions = parser.subscriptions;
         this.knownSubscriptions = knownSubscriptions;
         Filter.knownFilters = parser.knownFilters;
         Subscription.knownSubscriptions = parser.knownSubscriptions;
 
         if (!silent)
           filterNotifier.emit("load");
       }
     };
@@ -389,17 +360,17 @@
    * @return {Promise} promise resolved or rejected when loading is complete
    */
   loadFromDisk()
   {
     let tryBackup = backupIndex =>
     {
       return this.restoreBackup(backupIndex, true).then(() =>
       {
-        if (this.subscriptions.length == 0)
+        if (this.subscriptionCount == 0)
           return tryBackup(backupIndex + 1);
       }).catch(error =>
       {
         // Give up
       });
     };
 
     return IO.statFile(this.sourceFile).then(statData =>
@@ -409,17 +380,17 @@
         this.firstRun = true;
         return;
       }
 
       let parser = this.importData(true);
       return IO.readFromFile(this.sourceFile, parser).then(() =>
       {
         parser(null);
-        if (this.subscriptions.length == 0)
+        if (this.subscriptionCount == 0)
         {
           // No filter subscriptions in the file, this isn't right.
           throw new Error("No data in the file");
         }
       });
     }).catch(error =>
     {
       Cu.reportError(error);
@@ -463,17 +434,17 @@
   },
 
   /**
    * Generator serializing filter data and yielding it line by line.
    */
   *exportData()
   {
     // Do not persist external subscriptions
-    let subscriptions = this.subscriptions.filter(
+    let subscriptions = [...this.subscriptions()].filter(
       s => !(s instanceof ExternalSubscription)
     );
 
     yield "# Adblock Plus preferences";
     yield "version=" + formatVersion;
 
     let saved = new Set();
     let buf = [];