Add AudioStreamRegistry. Move stream counting logic

content/browser/renderer_host/media/audio_stream_registry_impl.cc

Index: content/browser/renderer_host/media/audio_stream_registry_impl.cc
diff --git a/content/browser/renderer_host/media/audio_stream_registry_impl.cc b/content/browser/renderer_host/media/audio_stream_registry_impl.cc
new file mode 100644
index 0000000000000000000000000000000000000000..97710e24d7eb538b34550f5b6ef02d2de3df0d23
--- /dev/null
+++ b/content/browser/renderer_host/media/audio_stream_registry_impl.cc
@@ -0,0 +1,95 @@
+// 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 "content/browser/renderer_host/media/audio_stream_registry_impl.h"
+
+#include <algorithm>
+
+#include "base/lazy_instance.h"
+#include "base/metrics/histogram_macros.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/render_process_host.h"
+#include "media/audio/audio_streams_tracker.h"
+
+namespace content {
+
+namespace {
+
+base::LazyInstance<media::AudioStreamsTracker> g_audio_output_streams_tracker =
+    LAZY_INSTANCE_INITIALIZER;
+
+void NotifyRenderProcessHostThatAudioStateChanged(int render_process_id) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+  RenderProcessHost* render_process_host =
+      RenderProcessHost::FromID(render_process_id);
+
+  if (render_process_host)
+    render_process_host->AudioStateChanged();
+}
+
+}  // namespace
+
+AudioStreamRegistryImpl::AudioStreamRegistryImpl(int render_process_id)
+    : render_process_id_(render_process_id) {}
+
+AudioStreamRegistryImpl::~AudioStreamRegistryImpl() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DCHECK(output_streams_.empty());
+
+  if (max_simultaneous_output_streams_ > 0) {
+    UMA_HISTOGRAM_CUSTOM_COUNTS("Media.AudioRendererIpcStreams",
+                                max_simultaneous_output_streams_, 1, 50, 51);
+    UMA_HISTOGRAM_CUSTOM_COUNTS(
+        "Media.AudioRendererIpcStreamsTotal",
+        g_audio_output_streams_tracker.Get().max_stream_count(), 1, 100, 101);
+    g_audio_output_streams_tracker.Get().ResetMaxStreamCount();
+  }
+}
+
+bool AudioStreamRegistryImpl::HasActiveAudio() {
+  return !base::AtomicRefCountIsZero(&num_playing_output_streams_);
+}
+
+void AudioStreamRegistryImpl::RegisterOutputStream(Stream* stream) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  output_streams_.insert(stream);

[o1ka, 2016/12/16 09:48:16]

DCheck that unique value is inserted?

[Max Morin, 2016/12/19 16:29:03]

Done.

+  max_simultaneous_output_streams_ =
+      std::max(max_simultaneous_output_streams_, output_streams_.size());
+  g_audio_output_streams_tracker.Get().IncreaseStreamCount();
+}
+
+void AudioStreamRegistryImpl::DeregisterOutputStream(Stream* stream) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  size_t num_erased = output_streams_.erase(stream);
+  DCHECK_EQ(num_erased, 1u);
+  g_audio_output_streams_tracker.Get().DecreaseStreamCount();
+}
+
+void AudioStreamRegistryImpl::OutputStreamStateChanged(bool playing) {

[o1ka, 2016/12/16 09:48:16]

Actually, to make it safer and more debuggable, we may want to store the current
state for each stream.

[Max Morin, 2016/12/19 16:29:03]

Done. (Debug only).

+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  if (playing) {
+    base::AtomicRefCountInc(&num_playing_output_streams_);
+
+    // Inform the RenderProcessHost when audio starts playing for the first
+    // time. The nonatomic increment-and-read is ok since this is the only
+    // thread that |num_playing_output_streams_| may be updated on.
+    if (base::AtomicRefCountIsOne(&num_playing_output_streams_)) {
+      BrowserThread::PostTask(
+          BrowserThread::UI, FROM_HERE,
+          base::Bind(&NotifyRenderProcessHostThatAudioStateChanged,
+                     render_process_id_));
+    }
+  } else {
+    // Inform the RenderProcessHost when there is no more audio playing.
+    if (!base::AtomicRefCountDec(&num_playing_output_streams_)) {

[o1ka, 2016/12/16 09:48:16]

Check that it's not below zero

[Max Morin, 2016/12/19 16:29:03]

Done.

+      BrowserThread::PostTask(
+          BrowserThread::UI, FROM_HERE,
+          base::Bind(&NotifyRenderProcessHostThatAudioStateChanged,
+                     render_process_id_));
+    }
+  }
+}
+
+}  // namespace content