Support abort(reason) call on AbortController.

[gxtaillon]

Motivation

Provide accurate error message when aborting fetch programmatically without user input.

Proposed Solution

Support abort(reason) call on AbortController.

Alternatives

None known to me.

Additional Context

Currently only abort() is supported. When using abort() on Chrome, cancelled fetch() calls return AbortError: The user aborted a request.. This is confusing when triggered without user input, for instance by timeouting early, or preemptively on navigation.

Best, gxt