The Audio Data Decoded All Event.
This event is dispatched by the Web Audio Sound Manager as a result of calling the decodeAudio method,
once all files passed to the method have been decoded (or errored).
Use Phaser.Sound.Events#DECODED to listen for single sounds being decoded, and DECODED_ALL to
listen for them all completing.
Listen to it from the Sound Manager in a Scene using this.sound.on('decodedall', listener), i.e.:
this.sound.once('decodedall', handler);
this.sound.decodeAudio([ audioFiles ]);