Google Docs viewer returning 204 responses, no longer working, alternatives?

Question

UPDATE 2016-11-16 9:53am EST

It appears many people are still seeing 204 responses even though Google has claimed to have \"fixed\" the problem. Wh

Answer 1

I was able to get this to work with Тетяна Волошка's answer, however I had to remove the if statement because

This

iframe.contentDocument.URL == "about:blank"

caused

DOMException: Blocked a frame with origin from accessing a cross-origin frame.

I'm not quite sure why this fixed it for me. Perhaps the 2 second delay allowed everything else on my page to load and remove any conflict for the embedded pdf to load, but how else could i get the content document without a the cross-origin issue?