Motown: Remove LPCM optimizations, fix prepare, add flush, add ActiveMultistreamSink model/stage

services/media/framework/parts/null_sink.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "services/media/framework/parts/null_sink.h"
 
 namespace mojo {
 namespace media {
 
 NullSink::NullSink() {}
 
 NullSink::~NullSink() {}
 
-bool NullSink::must_allocate() const {
-  return false;
-}
-
-Allocator* NullSink::allocator() {
+PayloadAllocator* NullSink::allocator() {
   return nullptr;
 }
 
-void NullSink::SetDemandCallback(DemandCallback demand_callback) {
+void NullSink::SetDemandCallback(const DemandCallback& demand_callback) {
   demand_callback_ = demand_callback;
 }
 
 void NullSink::Prime() {
   DCHECK(demand_callback_);
   demand_callback_(Demand::kNeutral);
 }
 
 Demand NullSink::SupplyPacket(PacketPtr packet) {
   return Demand::kNeutral;
 }
 
 } // namespace media
 } // namespace mojo