Relationship between XHR timeout and network timeout

[youennf]

XHR allows setting timeout.
There is probably interoperability when timeout is set.
It is unclear what happens when no timeout is set.

In WebKit, when timeout is set, the network IDLE timeout is disabled.
When no timeout is set, the default network IDLE timeout of 60 seconds may kick in.

Should there be a default XHR timeout value?

Related to fetch, no timeout mechanism is defined.
In WebKit, this would mean that the default network IDLE timeout of 60 seconds cannot be controlled by web developers.

[annevk]

Adding API surface to fetch() for timeouts is whatwg/fetch#20. Defining a default network timeout might be a thing we need to do at some point, but I think for now I'm okay with leaving that up to user agents unless we've found issues with that.