Add AudioStreamRegistry. Move stream counting logic

content/browser/renderer_host/media/audio_stream_registry_impl.h

+// 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.
+
+#ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_STREAM_REGISTRY_IMPL_H_
+#define CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_STREAM_REGISTRY_IMPL_H_
+
+#include <map>
+#include <memory>
+#include <set>
+
+#include "base/atomic_ref_count.h"
+#include "base/files/file_path.h"
+#include "base/macros.h"
+#include "base/threading/thread_checker.h"
+#include "content/browser/renderer_host/media/audio_stream_registry.h"
+#include "content/common/content_export.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace content {
+
+class CONTENT_EXPORT AudioStreamRegistryImpl : public AudioStreamRegistry {
+ public:
+  explicit AudioStreamRegistryImpl(int render_process_id);

[DaleCurtis, 2017/01/12 19:22:12]

Typically we don't expose both a normal constructor and a Create() method.

+  ~AudioStreamRegistryImpl() override;
+
+  using UniquePtr =
+      std::unique_ptr<AudioStreamRegistryImpl, BrowserThread::DeleteOnIOThread>;
+
+  static UniquePtr Create(int render_process_id);
+
+  // Indicates whether there is an output stream currently playing.
+  // May be called from any thread.
+  bool HasActiveAudio();
+
+  void RegisterStream() override;
+  void DeregisterStream() override;
+  void StreamStateChanged(bool playing) override;
+
+ private:
+  int32_t num_output_streams_ = 0;
+  int32_t max_simultaneous_output_streams_ = 0;
+  base::AtomicRefCount num_playing_output_streams_ = 0;
+  const int render_process_id_;
+};

[DaleCurtis, 2017/01/12 19:22:12]

DISALLOW_COPY_AND_ASSIGN

+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_STREAM_REGISTRY_IMPL_H_