feat(ext/http): abort event when request is cancelled (#26781)

```js
Deno.serve(async (req) => {
  const { promise, resolve } = Promise.withResolvers<void>();

  req.signal.addEventListener("abort", () => {
    resolve();
  });

  await promise;

  return new Response("Ok");
});
```

1 files changed, 13 insertions, 0 deletions

diff --git a/ext/http/http_next.rs b/ext/http/http_next.rs
index 326478fe7..c55e86835 100644
--- a/ext/http/http_next.rs
+++ b/ext/http/http_next.rs
@@ -708,6 +708,19 @@ pub fn op_http_get_request_cancelled(external: *const c_void) -> bool {
   http.cancelled()
 }
 
+#[op2(async)]
+pub async fn op_http_request_on_cancel(external: *const c_void) {
+  let http =
+    // SAFETY: op is called with external.
+    unsafe { clone_external!(external, "op_http_request_on_cancel") };
+  let (tx, rx) = tokio::sync::oneshot::channel();
+
+  http.on_cancel(tx);
+  drop(http);
+
+  rx.await.ok();
+}
+
 /// Returned promise resolves when body streaming finishes.
 /// Call [`op_http_close_after_finish`] when done with the external.
 #[op2(async)]