From 5c5da1d86f10294906ec8c6f117bb73aa06c46b9 Mon Sep 17 00:00:00 2001
From: Daniel Huigens <d.huigens@protonmail.com>
Date: Wed, 2 Jan 2019 14:07:36 +0100
Subject: [PATCH] Fix passing streams to workers in Safari 9

Safari 9 does not expose the MessagePort object in workers
(but does expose it on window, and also exposes MessageChannel
in workers).
---
 src/util.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/util.js b/src/util.js
index dbc8de3f..3a1f5f7e 100644
--- a/src/util.js
+++ b/src/util.js
@@ -88,7 +88,7 @@ export default {
           }
           return;
         }
-        if (typeof MessagePort !== 'undefined' && MessagePort.prototype.isPrototypeOf(value)) {
+        if (Object.prototype.toString.call(value) === '[object MessagePort]') {
           throw new Error("Can't transfer the same stream twice.");
         }
         util.collectTransferables(value, collection);
@@ -104,7 +104,7 @@ export default {
   restoreStreams: function(obj) {
     if (Object.prototype.isPrototypeOf(obj) && !Uint8Array.prototype.isPrototypeOf(obj)) {
       Object.entries(obj).forEach(([key, value]) => { // recursively search all children
-        if (MessagePort.prototype.isPrototypeOf(value)) {
+        if (Object.prototype.toString.call(value) === '[object MessagePort]') {
           obj[key] = new ReadableStream({
             pull(controller) {
               return new Promise(resolve => {