Fix URL constructor on udp:// urls in Chrome App environment

For: brave/brave-browser#5604

`bittorrent-tracker` is broken when run in a Chrome App environment.

The issue is that the `URL` constructor is buggy Chromium. https://bugs.chromium.org/p/chromium/issues/detail?id=734880

We switched to `URL` from `require('url')` in `[email protected]`. Commit: webtorrent@93b4139

This code path was not exercised by `bittorrent-tracker`'s tests because UDP trackers are normally only used in a Node.js environment. Braves run the code in a Chrome extension environment which we don't test.

Author: feross

lib/client/udp-tracker.js

@@ -71,7 +71,23 @@ class UDPTracker extends Tracker {
   _request (opts) {
     const self = this
     if (!opts) opts = {}
-    const parsedUrl = new URL(this.announceUrl)
+
+    // HACK: Fix for WHATWG URL object not parsing non-standard URL schemes like
+    // 'udp:'. Just replace it with 'http:' since we only need the `hostname`
+    // and `port` properties.
+    //
+    // Note: Only affects Chrome and Firefox. Works fine in Node.js, Safari, and
+    // Edge.
+    //
+    // Note: UDP trackers aren't used in the normal browser build, but they are
+    // used in a Chrome App build (i.e. by Brave Browser).
+    //
+    // Bug reports:
+    // - Chrome: https://bugs.chromium.org/p/chromium/issues/detail?id=734880
+    // - Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=1374505
+    let { hostname, port } = new URL(this.announceUrl.replace(/^udp:/, 'http:'))
+    if (port === '') port = 80
+
     let transactionId = genTransactionId()
     let socket = dgram.createSocket('udp4')
 
@@ -204,10 +220,7 @@ class UDPTracker extends Tracker {
     }
 
     function send (message) {
-      if (!parsedUrl.port) {
-        parsedUrl.port = 80
-      }
-      socket.send(message, 0, message.length, parsedUrl.port, parsedUrl.hostname)
+      socket.send(message, 0, message.length, port, hostname)
     }
 
     function announce (connectionId, opts) {