Add tests for ArrayBuffer detaching that throws and account for it in prose

[annevk]

As per whatwg/html#4601 DetachArrayBuffer can throw. There should be tests that this is handled adequately for all affected APIs (seem to be at least two from super quick skimming) and prose might need to be adjusted to indicate this is a thing. You might want to look at HTML for how this is handled.

Or perhaps IDL should be updated to handle this better somehow, not sure, but if so, comment at whatwg/webidl#724.

[padenot]

I've done related work in the past, taking this.

[rtoy]

Text needs to be updated for v1. Setting milestone to v1 for that.

[hoch]

For example, the step 2 of the algorithm for decodeAudioData(audioData, successCallback, errorCallback) we can capture the internal exception for an undetachable array and throw an error in the step 3.

[hoch]

For the acquiring the content procedure, we don't need to do anything because AudioBuffer's back-end ArrayBuffer is guaranteed to be detachable.

[annevk]

Guaranteed not to be detachable I take it?

[padenot]

No, this was correct:

• an AudioBuffer can only be instantiated using new AudioBuffer(...); or AudioContext.createBuffer(...);, this always allocate a normal ArrayBuffer ;
• This means that detaching cannot throw: either it's been detached already, and the operation returns false, or it worked, and it returns true.

[padenot]

Fixed by #1961.