WaveShaperNodeEngine::ProduceAudioBlock skips processing when input is null, but the resamplers may still have samples to play back from the previous block due to latency and filter effects. The total filter effect is just less than twice the latency, on both the upsample and downsample stages. These carry over samples are getting played back when the input becomes non-null again.

Mass change P2->P3 to align with new Mozilla triage process.