Widget Connector no longer works with Google Calendar

Summary

Per Widget Connector Macro you can insert the URL for a public Google Calendar. However, upon doing that, you get the image below:

Environment

• Confluence 6.0.0-OD-2016.10.1-1071
• Widget Connector 3.0.0

Steps to Reproduce

1. Create new page in Confluence
2. Type {Widget Connector and insert the required macro
3. Use URL to a Public Calendar that I created:

   https://calendar.google.com/calendar/embed?src=efisg1vnagrlup2bqkbblsn27k%40group.calendar.google.com&ctz=Europe/Amsterdam

Expected Results

Calendar should embed

Actual Results

Shows image that I displayed in the Summary.

Notes

May be related to CONF-40742

Workaround

1. In the editor, open the macro browser
2. Search for "iframe" and insert it
3. In the dialog, set the URL to calendar embed URL, I used the one included in this issue description.
4. Set the height/width to the dimensions you'd like.
5. Click "Insert"
6. Publish your page