<fb-popup-panel> received an inter-window message via window:message. The detail is the bridge's WindowMessagePayload, forwarded as is.
<fb-popup-panel>
window:message
WindowMessagePayload
The message as the sender passed it.
Window id of the message sender.
<fb-popup-panel>received an inter-window message viawindow:message. The detail is the bridge'sWindowMessagePayload, forwarded as is.