[kevincox]

The GMail web client definitely doesn't create an HTTP endpoint to receive updates. But the API it uses is likely proprietary and private (even if it was built on top of the public API there would be a backend bridging the two)

[dataflow]

Sorry, yes, my comment was confusing. I was answering the "how do I get faster notifications in a supported manner" part rather than the "how does the Gmail web UI do this" part.