Remove ie8/9 special CORS treatment and btoa polyfill

lib/adapters/xhr.js

@@ -6,7 +6,6 @@ var buildURL = require('./../helpers/buildURL');
 var parseHeaders = require('./../helpers/parseHeaders');
 var isURLSameOrigin = require('./../helpers/isURLSameOrigin');
 var createError = require('../core/createError');
-var btoa = (typeof window !== 'undefined' && window.btoa && window.btoa.bind(window)) || require('./../helpers/btoa');
 
 module.exports = function xhrAdapter(config) {
  return new Promise(function dispatchXhrRequest(resolve, reject) {
@@ -18,22 +17,6 @@ module.exports = function xhrAdapter(config) {
  }
 
  var request = new XMLHttpRequest();
- var loadEvent = 'onreadystatechange';
- var xDomain = false;
-
- // For IE 8/9 CORS support
- // Only supports POST and GET calls and doesn't returns the response headers.
- // DON'T do this for testing b/c XMLHttpRequest is mocked, not XDomainRequest.
- if (process.env.NODE_ENV !== 'test' &&
- typeof window !== 'undefined' &&
- window.XDomainRequest && !('withCredentials' in request) &&
- !isURLSameOrigin(config.url)) {
- request = new window.XDomainRequest();
- loadEvent = 'onload';
- xDomain = true;
- request.onprogress = function handleProgress() {};
- request.ontimeout = function handleTimeout() {};
- }
 
  // HTTP basic authentication
  if (config.auth) {
@@ -48,8 +31,8 @@ module.exports = function xhrAdapter(config) {
  request.timeout = config.timeout;
 
  // Listen for ready state
- request[loadEvent] = function handleLoad() {
- if (!request || (request.readyState !== 4 && !xDomain)) {
+ request.onreadystatechange = function handleLoad() {
+ if (!request || request.readyState !== 4) {
  return;
  }