Re: [w3ctag/design-reviews] Review OffscreenCanvas, including ImageBitmapRenderingContext (#141)

I'm not sure where to bring this up but under the current `OffscreenCanvas.commit()` proposal how are pages that are not the front tab handled?

With rAF the browser just doesn't call the callback.  With blocking commit though what's the plan?

* if `commit` blocks then the worker is stuck unable to process other events.
* if `commit` is a no-op then the worker is wasting time even though the user is not viewing the page and the canvas itsehas the wrong content 

I can imagine the following patterns with `commit`

1.   commit in spin loop

        // in worker

        while(true) {
            render();
            offscreenCanvas.commit();
        }

2.  commit in raf loop

         // in worker
         const socket = new WebSocket("ws://www.example.com/socketserver");
         socket.onmessage = handleMessagesFromServer;

         function loop() {
             render();
             requestAnimationFrame(loop);
             offscreenCanvas.commit();
         }
         requestAnimationFrame(loop);

In case 1 above blocking commit if the page is not the front page seems reasonable. In case 2 it does not because the worker was expecting to be able to process events. How will browsers be able to handle the 2 cases?

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