Same-site broadcast channel

[lghall]

Within Google Workspace, we have multiple applications which are on different sub-domains: for example, meet.google.com, docs.google.com, mail.google.com. Currently, if these applications want to communicate using a Broadcast Channel, we must proxy using an iframe which adds additional memory and latency overhead.

We propose adding a same-site broadcast channel, that sub-domains within the same top-level site (with proven mutual trust) could use for communication.