Issue 6066 - Implement 'force update' functionality for subscriptions

adblockplussbrowser/src/main/java/org/adblockplus/sbrowser/contentblocker/engine/Subscription.java

 /*
  * 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 46 matching lines @@
   public static final String KEY_TITLE = "title";
   public static final String KEY_VERSION = "version";
   public static final String KEY_HTTP_ETAG = "_etag";
   public static final String KEY_HTTP_LAST_MODIFIED = "_last_modified";
   public static final String KEY_UPDATE_TIMESTAMP = "_update_timestamp";
   public static final String KEY_TRIED_UPDATE_TIMESTAMP = "_tried_update_timestamp";
   public static final String KEY_DOWNLOAD_COUNT = "_download_count";
   public static final String KEY_ENABLED = "_enabled";
   public static final String KEY_META_HASH = "_meta_hash";
 
-  private static final long MINIMAL_DOWNLOAD_INTERVAL = DateUtils.HOUR_IN_MILLIS / 4;
+  private static final long MINIMAL_DOWNLOAD_INTERVAL = DateUtils.MINUTE_IN_MILLIS;

[jens, 2018/01/18 13:49:40]

I double-checked with felix and matze that a decrease of this threshold is fine.

   private static final long DOWNLOAD_RETRY_INTERVAL = DateUtils.HOUR_IN_MILLIS;
 
   /**
    * List of meta keys that are allowed to import from a downloaded
    * subscription.
    */
   private static final String[] ALLOWED_META_KEYS_ARRAY =
       {
           "checksum", KEY_VERSION, KEY_TITLE, "last modified", "expires", "homepage", "licence"
       };
@@ skipping 522 matching lines @@
     this.serializeMetaData(metaFile);
     if (filtersChanged)
     {
       this.serializeFilters(filtersFile);
       this.clearFilters();
     }
 
     return filtersChanged;
   }
 }