fix: remove safari-specific service worker code (#1712)

fixes #1595

src/routes/_utils/userAgent/isSafari.js

@@ -1,4 +0,0 @@
-import { thunk } from '../thunk'
-
-export const isSafari = thunk(() => process.browser && /Safari/.test(navigator.userAgent) &&
-  !/Chrome/.test(navigator.userAgent))

src/service-worker.js

@@ -4,7 +4,6 @@ import {
   routes as __routes__
 } from '../__sapper__/service-worker.js'
 import { get, post } from './routes/_utils/ajax'
-import { isSafari } from './routes/_utils/userAgent/isSafari'
 
 const timestamp = process.env.SAPPER_TIMESTAMP
 const ASSETS = `assets_${timestamp}`
@@ -86,30 +85,6 @@ self.addEventListener('activate', event => {
   })())
 })
 
-async function returnRangeRequest (request) {
-  const response = await fetch(request, { headers: {}, mode: 'cors', credentials: 'omit' })
-  const arrayBuffer = await response.arrayBuffer()
-  const bytes = /^bytes=(\d+)-(\d+)?$/g.exec(request.headers.get('range'))
-  if (bytes) {
-    const start = parseInt(bytes[1], 10)
-    const end = parseInt(bytes[2], 10) || arrayBuffer.byteLength - 1
-
-    return new Response(arrayBuffer.slice(start, end + 1), {
-      status: 206,
-      statusText: 'Partial Content',
-      headers: [
-        ['Content-Range', `bytes ${start}-${end}/${arrayBuffer.byteLength}`]
-      ]
-    })
-  } else {
-    return new Response(null, {
-      status: 416,
-      statusText: 'Range Not Satisfiable',
-      headers: [['Content-Range', `*/${arrayBuffer.byteLength}`]]
-    })
-  }
-}
-
 self.addEventListener('fetch', event => {
   const req = event.request
   const url = new URL(req.url)
@@ -154,14 +129,6 @@ self.addEventListener('fetch', event => {
     }
 
     // for everything else, go network-only
-
-    // range request need to be be patched with a 206 response to satisfy
-    // Safari (https://stackoverflow.com/questions/52087208)
-    // Once this bug is fixed in WebKit we can remove this https://bugs.webkit.org/show_bug.cgi?id=186050
-    if (isSafari() && event.request.headers.get('range')) {
-      return returnRangeRequest(req)
-    }
-
     return fetch(req)
   })())
 })