Audio asset throws `TypeError` when `preload="auto"` is used.

Description:

Hey, guys. I know you guys are hard at work on 0.9.0, but this issue has been plaguing some of us for some time and were hoping a fix could be managed in the next release.

Setting an <audio> asset within <a-assets> with preload="auto" (as documented at https://aframe.io/docs/master/components/sound.html#preloading-a-sound-asset) throws the following error:

Firefox 62.0.2 (Windows):

TypeError: Argument 1 of BaseAudioContext.decodeAudioData does not implement interface ArrayBuffer.[Learn More] three.js:37939:18 

Chrome 69.0.3497.100 (Windows):

three.js:37941 Uncaught (in promise) TypeError: Failed to execute 'decodeAudioData' on 'BaseAudioContext': parameter 1 is not of type 'ArrayBuffer'.
    at three.js:37941
    at three.js:30404

• A-Frame Version: 0.8.2
• Platform / Device: Reproduced in Firefox and Chrome on Windows 10 (only ones tested)
• Reproducible Code Snippet or URL:

Code:
https://glitch.com/edit/#!/aframe-audio-preload-bug

Demo:
https://aframe-audio-preload-bug.glitch.me/

I'm not sure if this is more of a THREE issue, but this is not working as documented. This makes it difficult to preload audio without maybe resorting to the use of autoplay on the audio source, which isn't ideal.

Looking forward to 0.9.0! Keep up the great work.

Thanks.

Start with the linked Glitch reproduction and demo, then read the sound component's preloading behavior described in the A-Frame sound documentation. Trace the three.js decodeAudioData call shown in the Firefox and Chrome errors to identify why preload="auto" supplies the wrong value. Done means the reproduction preloads the audio asset without a TypeError in both reported browsers.