Async scheme handlers

[kpko]

Since we have no support for wiring up javascript methods with callbacks for doing long running operations, I would like to use a custom scheme handler and do ajax calls, but the custom SchemeHandler is running on the UI-Thread and is blocking the execution of other calls to the SchemeHandler.

It would be great if we could provide an IAsyncSchemeHandler interface to implement asynchronous scheme handlers. I think the scheme handler mechanism in CEF already supports async operations because you can report data back from a call via a callback method in CEF.