--- a/browser/extensions/pdfjs/content/PdfStreamConverter.jsm
+++ b/browser/extensions/pdfjs/content/PdfStreamConverter.jsm
@@ -36,16 +36,18 @@ ChromeUtils.defineModuleGetter(this, "Pr
   "resource://gre/modules/PrivateBrowsingUtils.jsm");
 
 ChromeUtils.defineModuleGetter(this, "PdfJsTelemetry",
   "resource://pdf.js/PdfJsTelemetry.jsm");
 
 ChromeUtils.defineModuleGetter(this, "PdfjsContentUtils",
   "resource://pdf.js/PdfjsContentUtils.jsm");
 
+Cu.importGlobalProperties(["XMLHttpRequest"]);
+
 var Svc = {};
 XPCOMUtils.defineLazyServiceGetter(Svc, "mime",
                                    "@mozilla.org/mime;1",
                                    "nsIMIMEService");
 
 function getContainingBrowser(domWindow) {
   return domWindow.QueryInterface(Ci.nsIInterfaceRequestor)
                   .getInterface(Ci.nsIWebNavigation)
@@ -588,18 +590,16 @@ class RangedChromeActions extends Chrome
         if ("nsIPrivateBrowsingChannel" in Ci &&
             netChannel instanceof Ci.nsIPrivateBrowsingChannel) {
           var docIsPrivate = self.isInPrivateBrowsing();
           netChannel.setPrivate(docIsPrivate);
         }
       }
     };
     var getXhr = function getXhr() {
-      const XMLHttpRequest = Components.Constructor(
-          "@mozilla.org/xmlextras/xmlhttprequest;1");
       var xhr = new XMLHttpRequest();
       xhr.addEventListener("readystatechange", xhr_onreadystatechange);
       return xhr;
     };
 
     this.networkManager = new NetworkManager(this.pdfUrl, {
       httpHeaders: httpHeaderVisitor.headers,
       getXhr,