Add AudioStreamRegistry. Move stream counting logic

media/audio/audio_streams_tracker.cc

Index: media/audio/audio_streams_tracker.cc
diff --git a/media/audio/audio_streams_tracker.cc b/media/audio/audio_streams_tracker.cc
index 5363796df737f3667923479b192ddc709730c1a5..9f98aa0ffcf0b2b7376613fa0e3c63bc096a2b19 100644
--- a/media/audio/audio_streams_tracker.cc
+++ b/media/audio/audio_streams_tracker.cc
@@ -25,10 +25,10 @@ void AudioStreamsTracker::IncreaseStreamCount() {
     max_stream_count_ = current_stream_count_;
 }
 
-void AudioStreamsTracker::DecreaseStreamCount(size_t count) {
+void AudioStreamsTracker::DecreaseStreamCount() {
   DCHECK(thread_checker_.CalledOnValidThread());
-  DCHECK_GE(current_stream_count_, count);
-  current_stream_count_ -= count;
+  DCHECK_GE(current_stream_count_, static_cast<size_t>(1));
+  --current_stream_count_;
 }
 
 void AudioStreamsTracker::ResetMaxStreamCount() {