Issue 4775 - Fix subscription links for Firefox

subscriptionLink.postload.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 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 21 matching lines @@
     // Search the link associated with the click
     let link = event.target;
     while (!(link instanceof HTMLAnchorElement))
     {
       link = link.parentNode;
 
       if (!link)
         return;
     }
 
+    let queryString = null;

[kzar, 2017/01/28 12:35:01]

(The workaround that will apparently never die. Pretty sure I've removed and
re-added this several times already :/)

     if (link.protocol == "http:" || link.protocol == "https:")
     {
-      if (link.host != "subscribe.adblockplus.org" || link.pathname != "/")
-        return;
+      if (link.host == "subscribe.adblockplus.org" && link.pathname == "/")
+        queryString = link.search.substr(1);
     }
-    else if (!/^abp:\/*subscribe\/*\?/i.test(link.href))
+    else
+    {
+      // Firefox 51 doesn't seem to populate the "search" property for
+      // links with non-standard URL schemes so we need to extract the query
+      // string manually.
+      let match = /^abp:\/*subscribe\/*\?(.*)/i.exec(link.href);
+      if (match)
+        queryString = match[1];
+    }
+
+    if (!queryString)
       return;
 
     // This is our link - make sure the browser doesn't handle it
     event.preventDefault();
     event.stopPropagation();
 
     // Decode URL parameters
     let title = null;
     let url = null;
-    for (let param of link.search.substr(1).split("&"))
+    for (let param of queryString.split("&"))
     {
       let parts = param.split("=", 2);
       if (parts.length != 2 || !/\S/.test(parts[1]))
         continue;
       switch (parts[0])
       {
         case "title":
           title = decodeURIComponent(parts[1]);
           break;
         case "location":
@@ skipping 15 matching lines @@
       return;
 
     ext.backgroundPage.sendMessage({
       type: "subscriptions.add",
       title: title,
       url: url,
       confirm: true
     });
   }, true);
 }