Switch stream creation and closing in Chrome audio rendering from IPC to Mojo

content/browser/media/audio_output_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_MEDIA_AUDIO_OUTPUT_IMPL_H_
+#define CONTENT_BROWSER_MEDIA_AUDIO_OUTPUT_IMPL_H_
+
+#include "base/callback.h"
+#include "base/sync_socket.h"
+#include "content/browser/renderer_host/media/audio_renderer_host.h"
+#include "media/mojo/interfaces/audio_output.mojom.h"
+#include "mojo/public/cpp/bindings/interface_request.h"
+#include "mojo/public/cpp/bindings/strong_binding.h"
+
+namespace content {
+class AudioOutputStreamImpl;
+
+// This class implements AudioOutput Mojo interface. It will be used
+// by the AudioOutputClient to perform operations on audio output streams.
+// AudioOutputClient is going to perform operations remotely and Mojo will
+// transfer them to AudioOutputImpl.
+// This class must always be accessed from the creation thread.
+class CONTENT_EXPORT AudioOutputImpl
+    : NON_EXPORTED_BASE(public media::mojom::AudioOutput) {
+ public:
+  explicit AudioOutputImpl(RenderProcessHost* process_,
+                           int render_frame_id,
+                           media::mojom::AudioOutputRequest request);
+
+  ~AudioOutputImpl() override;
+
+  // Creates a Mojo service.
+  static void CreateService(RenderProcessHost* process_,
+                            int render_frame_id,
+                            media::mojom::AudioOutputRequest request);
+  // Initialized Mojo service on the IO thread. The service is bound to the
+  // IO thread so future Mojo calls performed by the AudioOutputClient to the
+  // AudioOutput interface will be run on that thread.
+  // There are a lot of dependencies used in audio output that require to be
+  // called on the IO thread, this is why we initialize Mojo service on this
+  // thread. There is a plan to enable these dependencies to run on another
+  // thread and move the Mojo service to this thread as IO thread is very
+  // performance sensitive and we want to move stuff off it.
+  static void CreateServiceOnIOThread(RenderProcessHost* process_,
+                                      int render_frame_id,
+                                      media::mojom::AudioOutputRequest request);
+
+  // Called by AudioRendererHost::DoCompleteCreation to create the streams.

[DaleCurtis, 2016/05/23 20:50:37]

This should just be CreateStream() StreamFactory isn't helpful.

[rchtara, 2016/05/24 17:25:55]

Unfortunately, here the socket and shared memory required to be returned using
the callback are not created yet. As the AudioOutputImpl::CreateStream will call
asynchronously AudioRendererHost::DoCompleteCreation  (it includes calling
AudioOutputController::Create which goes to the  controller->message_loop_)
And that's when everything is ready for the stream creation, and this why
StreamFactory is needed.
So we need a way to store the callback, to use it
AudioOutputImpl::StreamFactory.
We could pass it as an argument to AudioRendererHost::OnCreateStream and pass it
around from a function to another and get it back when we are in the
DoCompleteCreation  then send it to AudioOutputImpl::StreamFactory, but we need
to change a lot of functions: (see the functions that are going to be changed, I
didn't  include the ones related to AudioOutputController::OnDeviceChange.)

AudioRendererHost::OnCreateStream
 AudioRendererHost::DoCreateStream
AudioRendererHost::AudioEntry::AudioEntry()

AudioOutputController::OnDeviceChange()  and  AudioOutputController::Create

 AudioOutputController::DoCreate 
AudioEntry::OnCreated() =>
 AudioRendererHost::DoCompleteCreation 
AudioOutputImpl::StreamFactory

So, I think storing the callback in a map is the best option for now.

+  virtual void StreamFactory(
+      int stream_id,
+      base::SharedMemory* shared_memory,
+      base::SyncSocket::TransitDescriptor socket_descriptor);
+
+  virtual bool CloseStream(int stream_id);
+  // Send an error message to the renderer, then close the stream.
+  virtual void ReportErrorAndCloseStream(int stream_id);
+
+ private:
+  friend class AudioOutputImplTest;
+  friend class MockAudioOutputImpl;
+  FRIEND_TEST_ALL_PREFIXES(AudioOutputImplTest, CreateStream);
+  FRIEND_TEST_ALL_PREFIXES(AudioOutputImplTest, StreamFactory);
+  FRIEND_TEST_ALL_PREFIXES(AudioOutputImplTest, RemoveStream);
+
+  static void Disconnect(int process_id, int render_frame_id);
+
+  // AudioOutput interface implementation.
+  void CreateStream(int stream_id,
+                    const media::AudioParameters& params,
+                    const CreateStreamCallback& callback) override;
+
+  RenderProcessHost* process_;
+  int render_frame_id_;
+  mojo::Binding<AudioOutput> binding_;
+  std::map<int, std::unique_ptr<AudioOutputStreamImpl>> stream_impls_;
+  std::map<int, media::mojom::AudioOutput::CreateStreamCallback>
+      create_stream_callbacks_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioOutputImpl);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_MEDIA_AUDIO_OUTPUT_IMPL_H_