Update fetch to latest https://github.com/github/fetch

Summary:This fixes https://github.com/facebook/react-native/issues/6326 with updating https://github.com/facebook/react-native/blob/master/Libraries/Fetch/fetch.js to latest from  https://github.com/github/fetch.

cc skevy steveluscher
Closes https://github.com/facebook/react-native/pull/6347

Differential Revision: D3024308

Pulled By: davidaurelio

fb-gh-sync-id: da87827b94d683aeb66be345e255bd771fdba1be
shipit-source-id: da87827b94d683aeb66be345e255bd771fdba1be

Libraries/Fetch/fetch.js

@@ -159,13 +159,13 @@ var self = {};
         return false
       }
     })(),
-    formData: typeof FormData === 'function'
+    formData: typeof FormData === 'function',
+    arrayBuffer: typeof ArrayBuffer === 'function'
   }
 
   function Body() {
     this.bodyUsed = false
 
-
     this._initBody = function(body) {
       this._bodyInit = body
       if (typeof body === 'string') {
@@ -176,9 +176,20 @@ var self = {};
         this._bodyFormData = body
       } else if (!body) {
         this._bodyText = ''
+      } else if (support.arrayBuffer && ArrayBuffer.prototype.isPrototypeOf(body)) {
+        // Only support ArrayBuffers for POST method.
+        // Receiving ArrayBuffers happens via Blobs, instead.
       } else {
         throw new Error('unsupported BodyInit type')
       }
+
+      if (!this.headers.get('content-type')) {
+        if (typeof body === 'string') {
+          this.headers.set('content-type', 'text/plain;charset=UTF-8')
+        } else if (this._bodyBlob && this._bodyBlob.type) {
+          this.headers.set('content-type', this._bodyBlob.type)
+        }
+      }
     }
 
     if (support.blob) {
@@ -315,15 +326,15 @@ var self = {};
       options = {}
     }
 
-    this._initBody(bodyInit)
     this.type = 'default'
-    this.url = null
     this.status = options.status
     this.ok = this.status >= 200 && this.status < 300
     this.statusText = options.statusText
     this.headers = options.headers instanceof Headers ? options.headers : new Headers(options.headers)
     this.url = options.url || ''
+    this._initBody(bodyInit)
   }
+  Body.call(Response.prototype)
 
   Response.prototype.clone = function() {
     return new Response(this._bodyInit, {
@@ -334,13 +345,28 @@ var self = {};
     })
   }
 
-  Body.call(Response.prototype)
+  Response.error = function() {
+    var response = new Response(null, {status: 0, statusText: ''})
+    response.type = 'error'
+    return response
+  }
+
+  var redirectStatuses = [301, 302, 303, 307, 308]
+
+  Response.redirect = function(url, status) {
+    if (redirectStatuses.indexOf(status) === -1) {
+      throw new RangeError('Invalid status code')
+    }
+
+    return new Response(null, {status: status, headers: {location: url}})
+  }
 
   self.Headers = Headers;
   self.Request = Request;
   self.Response = Response;
 
   self.fetch = function(input, init) {
+    return new Promise(function(resolve, reject) {
       var request
       if (Request.prototype.isPrototypeOf(input) && !init) {
         request = input
@@ -348,7 +374,6 @@ var self = {};
         request = new Request(input, init)
       }
 
-    return new Promise(function(resolve, reject) {
       var xhr = new XMLHttpRequest()
 
       function responseURL() {
@@ -365,13 +390,8 @@ var self = {};
       }
 
       xhr.onload = function() {
-        var status = (xhr.status === 1223) ? 204 : xhr.status
-        if (status < 100 || status > 599) {
-          reject(new TypeError('Network request failed'))
-          return
-        }
         var options = {
-          status: status,
+          status: xhr.status,
           statusText: xhr.statusText,
           headers: headers(xhr),
           url: responseURL()
@@ -405,5 +425,4 @@ var self = {};
 })();
 
 /** End of the third-party code */
-
 module.exports = self;