Animation-bound sound keeps playing after the animation stops

[nighca]

Background

In spx, an animation can bind to a sound so that the sound is played automatically while the animation is playing.

There is currently a bug in this behavior: after the animation stops, the bound sound does not stop with it and keeps playing.

Reproduction

A reproducible example is available here:

• https://x.qiniu.com/project/nighca/niu-run

Steps:

1. Open the project above
2. Click somewhere on the grass so the cow starts walking toward that position
3. Wait until the cow finishes walking

Actual behavior

• The walking animation stops
• The walking sound keeps playing after the animation has already stopped

Expected behavior

• The walking sound should stop when the animation stops
• After the cow finishes walking, there should no longer be any walking sound

Notes

This issue is about animation-bound sound lifecycle. If a sound is started automatically because of an animation binding, it should also stop automatically when that animation ends.

[nighca]

@joeykchen 我想起来这个可能不是 bug，可能是预期的行为（不太好确定是因为之前做的时候预期行为没有落 spec）

可以先帮从实现上确认下老版本的 spx（如 1.x）的行为，如果老版本 spx 也是这个行为（animation 停止后 sound 不停止播放），那应该就是当初的“预期行为”，具体要不要改我们还要再讨论下；如果老版本的 spx 会在 sound 停止时停止播放 sound，那我们就跟老版本一致。