I have axios@0.15.2

If this HTML is run, some requests will be cancelled by Chrome:

    <html>
    <head>
        <script src="https://cdnjs.cloudflare.com/ajax/libs/axios/0.15.2/axios.js"></script>
    </head>
        <script>
        var promises = [];
        window.onload = function() {
            for (var i = 0; i < 4; i++) {
                var promise = axios.get('some url which causes ERR_CONNECTION_CLOSED');
                promises.push(promise);
            }
        }
       </script>
    </html>

![Cancelled](https://cloud.githubusercontent.com/assets/4506837/20349972/9123cef0-ac2e-11e6-93db-0ec66f205382.png)

But promises which turned into cancelled request won't be fulfilled:

![notfulfilled](https://cloud.githubusercontent.com/assets/4506837/20350023/d2146c4e-ac2e-11e6-89bc-983233628d09.png)

lib/adapters/xhr.js
var settle = require('./../core/settle');
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) {
    var requestData = config.data;
    var requestHeaders = config.headers;
    if (utils.isFormData(requestData)) {
      delete requestHeaders['Content-Type']; 
    }
    var request = new XMLHttpRequest();
    var loadEvent = 'onreadystatechange';
    var xDomain = false;
    
    
    
    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() {};
    }