Make prefetching works again. (#422)

client/next-prefetcher.js

@@ -51,7 +51,10 @@ function sendReply (e, result) {
 
 function cacheUrl (url) {
   const req = new self.Request(url, {
-    mode: 'no-cors'
+    mode: 'no-cors',
+    headers: {
+      'Accept': 'application/json'
+    }
   })
 
   return self.caches.open(CACHE_NAME)

lib/prefetch.js

@@ -108,11 +108,8 @@ export function prefetch (href) {
 
   let { pathname } = urlParse(href)
   // Add support for the index page
-  if (pathname === '/') {
-    pathname = '/index'
-  }
 
-  const url = `${pathname}.json`
+  const url = `/_next/pages${pathname}`
   if (PREFETCHED_URLS[url]) return
 
   messenger.send({ action: 'ADD_URL', url: url })