Better feature detection for FormData/FileReader/Blob

Summary: This PR bumps fetch to 0.9.0, the latest release and fixes broken feature detection originating in that self is not referring to `window.self` but an empty object. Assigning that object to window.self or GLOBAL won't work in the chrome dev tools because of CORS restrictions. This is a pragmatic solution but maybe not ideal.

Background to the problem can be read here: https://github.com/facebook/react-native/issues/2376
Closes https://github.com/facebook/react-native/pull/2587

Reviewed By: @​trunkagent, @​svcscm

Differential Revision: D2438341

Pulled By: @vjeux

Libraries/Fetch/fetch.js

@@ -50,7 +50,7 @@ var self = {};
 
   function normalizeName(name) {
     if (typeof name !== 'string') {
-      name = name.toString();
+      name = String(name)
     }
     if (/[^a-z0-9\-#$%&'*+.\^_`|~]/i.test(name)) {
       throw new TypeError('Invalid character in header field name')
@@ -60,7 +60,7 @@ var self = {};
 
   function normalizeValue(value) {
     if (typeof value !== 'string') {
-      value = value.toString();
+      value = String(value)
     }
     return value
   }
@@ -68,18 +68,15 @@ var self = {};
   function Headers(headers) {
     this.map = {}
 
-    var self = this
     if (headers instanceof Headers) {
-      headers.forEach(function(name, values) {
+      headers.forEach(function(value, name) {
-        values.forEach(function(value) {
+        this.append(name, value)
-          self.append(name, value)
+      }, this)
-        })
-      })
 
     } else if (headers) {
       Object.getOwnPropertyNames(headers).forEach(function(name) {
-        self.append(name, headers[name])
+        this.append(name, headers[name])
-      })
+      }, this)
     }
   }
 
@@ -115,12 +112,12 @@ var self = {};
     this.map[normalizeName(name)] = [normalizeValue(value)]
   }
 
-  // Instead of iterable for now.
+  Headers.prototype.forEach = function(callback, thisArg) {
-  Headers.prototype.forEach = function(callback) {
-    var self = this
     Object.getOwnPropertyNames(this.map).forEach(function(name) {
-      callback(name, self.map[name])
+      this.map[name].forEach(function(value) {
-    })
+        callback.call(thisArg, value, name, this)
+      }, this)
+    }, this)
   }
 
   function consumed(body) {
@@ -154,7 +151,7 @@ var self = {};
   }
 
   var support = {
-    blob: 'FileReader' in self && 'Blob' in self && (function() {
+    blob: typeof FileReader === 'function' && typeof Blob === 'function' && (function() {
       try {
         new Blob();
         return true
@@ -162,7 +159,7 @@ var self = {};
         return false
       }
     })(),
-    formData: 'FormData' in self
+    formData: typeof FormData === 'function'
   }
 
   function Body() {
@@ -246,20 +243,40 @@ var self = {};
     return (methods.indexOf(upcased) > -1) ? upcased : method
   }
 
-  function Request(url, options) {
+  function Request(input, options) {
     options = options || {}
-    this.url = url
+    var body = options.body
+    if (Request.prototype.isPrototypeOf(input)) {
+      if (input.bodyUsed) {
+        throw new TypeError('Already read')
+      }
+      this.url = input.url
+      this.credentials = input.credentials
+      if (!options.headers) {
+        this.headers = new Headers(input.headers)
+      }
+      this.method = input.method
+      this.mode = input.mode
+      if (!body) {
+        body = input._bodyInit
+        input.bodyUsed = true
+      }
+    } else {
+      this.url = input
+    }
 
-    this.credentials = options.credentials || 'omit'
+    this.credentials = options.credentials || this.credentials || 'omit'
-    this.headers = new Headers(options.headers)
+    if (options.headers || !this.headers) {
-    this.method = normalizeMethod(options.method || 'GET')
+      this.headers = new Headers(options.headers)
-    this.mode = options.mode || null
+    }
+    this.method = normalizeMethod(options.method || this.method || 'GET')
+    this.mode = options.mode || this.mode || null
     this.referrer = null
 
-    if ((this.method === 'GET' || this.method === 'HEAD') && options.body) {
+    if ((this.method === 'GET' || this.method === 'HEAD') && body) {
       throw new TypeError('Body not allowed for GET or HEAD requests')
     }
-    this._initBody(options.body)
+    this._initBody(body)
   }
 
   function decode(body) {
@@ -311,7 +328,6 @@ var self = {};
   self.Response = Response;
 
   self.fetch = function(input, init) {
-    // TODO: Request constructor should accept input, init
     var request
     if (Request.prototype.isPrototypeOf(input) && !init) {
       request = input
@@ -321,9 +337,6 @@ var self = {};
 
     return new Promise(function(resolve, reject) {
       var xhr = new XMLHttpRequest()
-      if (request.credentials === 'cors') {
-        xhr.withCredentials = true;
-      }
 
       function responseURL() {
         if ('responseURL' in xhr) {
@@ -360,14 +373,16 @@ var self = {};
 
       xhr.open(request.method, request.url, true)
 
+      if (request.credentials === 'include') {
+        xhr.withCredentials = true
+      }
+
       if ('responseType' in xhr && support.blob) {
         xhr.responseType = 'blob'
       }
 
-      request.headers.forEach(function(name, values) {
+      request.headers.forEach(function(value, name) {
-        values.forEach(function(value) {
+        xhr.setRequestHeader(name, value)
-          xhr.setRequestHeader(name, value)
-        })
       })
 
       xhr.send(typeof request._bodyInit === 'undefined' ? null : request._bodyInit)