Add AudioStreamRegistry. Move stream counting logic

content/browser/renderer_host/media/audio_stream_registry.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_H_
+#define CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_STREAM_REGISTRY_H_
+
+#include "media/media_features.h"
+
+namespace base {
+class FilePath;
+}
+
+namespace content {
+
+// This class tracks all the input and output streams and enables stream

[o1ka, 2016/12/22 10:46:52]

Debug recording is enabled/disabled for all hosts at once. (We need to check if
there are are any plans/usecases to operate per host there). It should be a Mojo
interface to audio process.
We may need to have a single AudioStreamRegistry for all hosts; we won't have
ARH in Mojo audio process.

BTW, we missed AecDumpMsg_EnableAecDump from renderer/browser Mojo interfaces.

We need to design debug recording interactions before proceeding with this CL.
(But we may want to split stream counting/debug recording into separate CLs when
it comes to implementation)

- Sorry, I did not realize some aspects in the first review round.

[Max Morin, 2017/01/09 15:34:23]

Browser will need an interface to each individual stream (since it must supply
file descriptors), so the UI can just iterate over all the stream and enable
debug recording for each one.
AudioStreamRegistry stays in browser process (see other comment).
Right. If the new output debug recording will be controlled by the AudioManager,
we can just scrap the debug recording stuff in this CL.

[o1ka, 2017/01/10 11:47:40]

Ah ok, now I see. Fine then!
Let's keep debug recording in a separate CL, to pair it with input one.

+// counting and debug recording controll for the RenderProcessHost. Methods
+// may only be called on the IO thread.
+class AudioStreamRegistry {
+ public:
+  class Stream {
+   public:
+    virtual ~Stream() {}
+
+#if BUILDFLAG(ENABLE_WEBRTC)
+    // The stream is expected to add a suffix to this file name, making it
+    // unique.
+    virtual void EnableDebugRecording(const base::FilePath& base_file_name) = 0;
+    virtual void DisableDebugRecording() = 0;
+#endif  // BUILDFLAG(ENABLE_WEBRTC)
+  };
+
+  virtual ~AudioStreamRegistry() {}
+
+  // Streams must be removed before destruction.
+  // virtual void RegisterInputStream(Stream* stream) = 0;
+  virtual void RegisterOutputStream(Stream* stream) = 0;
+  // virtual void DeregisterInputStream(Stream* stream) = 0;
+  virtual void DeregisterOutputStream(Stream* stream) = 0;
+
+  virtual void OutputStreamStateChanged(Stream* stream, bool playing) = 0;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_STREAM_REGISTRY_H_