Make FirefoxCom.requestSync able to return objects from PdfStreamConverter.jsm, by utilizing makeContentReadable

extensions/firefox/content/PdfStreamConverter.jsm

@@ -794,7 +794,7 @@ RequestListener.prototype.receive = function(event) {
   var response;
   if (sync) {
     response = actions[action].call(this.actions, data);
-    event.detail.response = response;
+    event.detail.response = makeContentReadable(response, doc.defaultView);
   } else {
     if (!event.detail.responseExpected) {
       doc.documentElement.removeChild(message);