Bug 277321 – stream not cancelled when seeking video(except for the first time)

• Component: Media
• Status: NEW

Created attachment 472012 [details]
this video display the issue

I am using a video element to play m3u8 and using a Service Worker to intercept mpeg-ts segment requests. To detect when a segment request is canceled upon video seeking, I return each segment as a ReadableStream. When seeking, the video needs to cancel the currently ongoing segment request and request new segments. At this point, the currently canceled segment triggers stream.cancel(). However, I found that only the first seek cancels the segment request and triggers the cancel event. When I seek again, the currently ongoing segment request is not canceled, nor does it trigger the cancel event. It's as if everything gets stuck, just like shown in the video.

my Service Worker code：

```

self.addEventListener("fetch", (event) => {

  const requestUrl = event.request.url;
  if (requestUrl.indexOf('.ts') === -1) return;

  console.log('fragment request', event.request.url)

  event.respondWith((async () => {
    const stream = new ReadableStream({
      start(controller) {
        console.log('start called', controller);
      },
      cancel(reason) {
        console.log('cancel called', reason);
      }
    });
    return new Response(stream);
  })());

})
```

Created attachment 472013 [details]
demo

here is the demo code

[Radar WebKit Bug Importer]

<rdar://problem/133266080>