Chrome Version       : 63.0.3239.30 (Official Build) beta (64-bit) (cohort: Beta)
URLs (if applicable) :
Other browsers tested:
  Add OK or FAIL, along with the version, after other browsers where you
have tested this issue:
    Chrome: OK 62.0.3202.75 
    Firefox: OK 45.0.1 ESR

What steps will reproduce the problem?
(0) Ensure using chrome 63 (beta) and have NodeJS install (or setup own server)
(1) Unzip attached file
(2) NPM install (simple express server) (ive zipped up the node module)
(3) Run node index.js
(4) got to localhost:3000
(5) Open dev tools
(6) Observe i have a long running XHR (will run every 30 secs)
(7) Note i am running this from an iframe (this is important to the problem)
(8) Click the "open app" button
(9)A new tab is immediately opened, which will postMessage back to the window.opener, it will then perform an XHR request, and upon response should update the location of the page
(10) The short XHR request will await the response of the long running /listen request (it shouldnt)
(11) Eventually the browser will redirect (if you switch tabs back to localhost:3000/ the request will finish and redirect.
(12) if you go to localhost:3000/iframe (this is the same page in index just not embedded) you will see the redirect immediately (correct behavior)

The code:
index.html -> embeds iframe.html
iframe.html -> opens a new tab and performs some XHRs
index.js -> serves app and responds to long running /listen request


What is the expected result?
When the tab is opened an XHR should be performed after posting back to the opener, and when the XHR responds the page is redirected to google.co.uk.
It seems like when running inside of an iframe and the tab has lost focus can only seem to make one request, or something like this.


What happens instead?
The short XHR that should respond immediately appears to be blocked until the long running /listen request responds.

Please provide any additional information below. Attach a screenshot if
possible.

Attached animated gifs

 

Deleted: problem.gif 1.6 MB

	problem.gif 1.6 MB View Download

Deleted: newTab.zip 628 KB

newTab.zip 628 KB Download

Deleted: working.gif 764 KB

	working.gif 764 KB View Download

Deleted: switching_tabs.gif 907 KB

	switching_tabs.gif 907 KB View Download