Update to constructor operations

[Ms2ger]

See whatwg/webidl#778.

[rtoy]

The important part is whatwg/webidl#636. Basically, we have

[Exposed=Window,
 Constructor (BaseAudioContext context, optional AnalyserOptions options = {})]
interface AnalyserNode : AudioNode {
...
}

and the proposal is to make this

[Exposed=Window]
interface AnalyserNode : AudioNode {
  constructor(BaseAudioContext context, optional AnalyserOptions options = {});
...
}