This is the "Compose a Replacement" dialog box shown in Web X-Ray Goggles when the user presses "R" to remix the currently focused element.
Check out the Web X-Ray Goggles repository in the root of this repo, and make
sure its directory is called webxray.
Then just run python server.py and visit http://127.0.0.1:8002/ to manually
test the dialog with sample data.
To run the unit tests, visit http://localhost:8002/test/.
To use the dialog with the goggles, see the webxray repository instructions. For reference, your hosted instance of the dialog is at http://localhost:8002/.
When the dialog is opened in an iframe by the goggles, it's passed arbitrary HTML (whatever the user has selected with the goggles) via postMessage and injected into the dialog for live editing by the user. This means that the domain the dialog is served from shouldn't contain any sensitive information; preferably, it should only be used to serve this dialog.