Import from Google Docs is not working for instances named *.jira.com

Issue Summary

On Confluence Cloud, it's possible to create a page importing a Google Document. However, this functionality is not working as expected on Instances which the URL is .jira.com *(instead of .atlassian.net*).

Steps to Reproduce

1. Access an Instance with this URL structure.
2. Click on Create a page (make sure that the Instance has the new template gallery).
3. Switch to Import tab.
4. Select Google Doc.
5. Authenticate to the Google account that has the desired document.

Expected Results

After authenticating the user, the Instance should prompt a list with the Documents from this Google account, so the user can choose the desired one.

Actual Results

User is prompted with below error message:

Below error is thrown on browser console:

Failed to execute 'postMessage' on 'DOMWindow': The target origin provided ('https://docs.google.com') does not match the recipient window's origin ('https://<INSTANCE>.jira.com').  

Workaround

Engage Atlassian Support, so we can edit some settings on the Google integration.