Customizer: Separate message url from preview url in customizer JS Previewer and PreviewFrame objects
|Reported by:||koopersmith||Owned by:||koopersmith|
Currently, the message url and preview url are cobbled together inside the previewer — this worked when we did not have robust PreviewFrame objects. However, now that we have first class preview objects, we need to properly distinguish between the url the messages are sent over (the control url, because we're using dynamically created iframes), and the URL of the preview request.
Without this, cross-domain requests are failing based on origin mismatches, which is bad. Patch coming soon.