VideoTexture: Make use of requestVideoFrameCallback().

[Mugen87]

Replacement of #19905.

This makes the WebGL warnings in webgl_video_panorama_equirectangular go away.

[Mugen87]

As mentioned here #19905 (comment), when the support of requestVideoFrameCallback() gets better, VideoTexture.update() can be removed.

Current support status: https://caniuse.com/#search=requestVideoFrameCallback

[mrdoob]

Thanks!

[mrdoob]

Feels good to only update video textures when needed. Finally...

[mrdoob]

@greggman do you think I should revert 95db034?

[greggman]

No I don't think so you should revert it. This 95db034 a different issue than #19905

[greggman]

Or maybe revert is the wrong suggestion. originally it was arguably wrong in that the event it was waiting for could have already happened. Maybe with the new fix it doesn't need the event at all?

[mrdoob]

Or maybe revert is the wrong suggestion. originally it was arguably wrong in that the event it was waiting for could have already happened. Maybe with the new fix it doesn't need the event at all?

Yes, that's what I meant.