Over Christmas I implemented some code to open a channel to my App Engine application using the channel API and it was working fine.
I recently returned to the code and find that it is broken, and the problem seems to lie in talkgadget that the client code is trying to load into a frame.
I took a snapshot of the code returned by /_ah/channel/jsapi on December 21 and I am comparing it to today's code.
When the older version tried to get talkgadget.google.com/talkgadget/d?token=[my-token] it was hardcoded to use http. Sensibly enough, the code was later changed to check the page's protocol in document.location and adapt to cases where https is used. The problem now is that when running in a chrome extension it grabs chrome-extension: as the protocol and naturally the channel fails to open in the extension.
Setting the base of the background page to my appspot URL does not change document.location, although I had some vague notion that it should. (Not sure what the standards say.)
Is there a workaround for this? One thought was to create my own iframe loaded from my site, but then it will nest the actual channel iframe, complicating things.
I wonder if Moishe or someone else on the App Engine team could comment on this. It seems like the this is a bug and the code should take into chrome extensions either by testing for the protocol and searching for a base tag as an alternative, or provide some way to configure this through the javascript object.
Yep, this is a bug. There's a fix submitted, and it's in the process of rolling out to production; it'll probably be out in about a week.
In the meantime, your idea of an iframe embedded in the extension should work.