Similar to the neutering behavior for decodeAudioData's argument, we need to precisely define what happens when script attempts to access or modify AudioProcessingEvent.outputBuffer after the event has been dispatched.  The most efficient way to handle this would be to neuter the array buffers in outputBuffer so that the implementation can use the buffer without having to copy its data to an internal buffer in order to avoid being affected by any possible modifications coming from content after the event has been dispatched.