MediaStream audio: Refactor 3 separate "glue" implementations into one.

content/renderer/media/external_media_stream_audio_source.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_RENDERER_MEDIA_MEDIA_INTERFACE_PROVIDER_H_
-#define CONTENT_RENDERER_MEDIA_MEDIA_INTERFACE_PROVIDER_H_
+#ifndef CONTENT_RENDERER_MEDIA_EXTERNAL_MEDIA_STREAM_AUDIO_SOURCE_H_
+#define CONTENT_RENDERER_MEDIA_EXTERNAL_MEDIA_STREAM_AUDIO_SOURCE_H_
 
-#include "base/callback.h"
-#include "base/macros.h"
-#include "base/threading/thread_checker.h"
-#include "content/common/content_export.h"
-#include "media/mojo/interfaces/service_factory.mojom.h"
-#include "mojo/shell/public/interfaces/interface_provider.mojom.h"
-#include "url/gurl.h"
+#include "content/renderer/media/media_stream_audio_source.h"
+
+#include "media/base/audio_capturer_source.h"
 
 namespace content {
 
-// MediaInterfaceProvider is an implementation of mojo InterfaceProvider that
-// provides media related services and handles app disconnection automatically.
-// This class is single threaded.
-class CONTENT_EXPORT MediaInterfaceProvider
-    : public mojo::shell::mojom::InterfaceProvider {
+// Represents an externally-provided local or remote source of audio data.  This
+// allows users of the public content::MediaStreamApi to provide a
+// media::AudioCapturerSource to be used as the source of audio data in the
+// MediaStream framework.  Audio data is transported directly to the tracks
+// (i.e., there is no audio processing).
+class CONTENT_EXPORT ExternalMediaStreamAudioSource final
+    : NON_EXPORTED_BASE(public MediaStreamAudioSource),
+      NON_EXPORTED_BASE(public media::AudioCapturerSource::CaptureCallback) {
  public:
-  // Callback used to connect to a mojo application.
-  using ConnectToApplicationCB =
-      base::Callback<mojo::shell::mojom::InterfaceProviderPtr(const GURL& url)>;
+  ExternalMediaStreamAudioSource(
+      scoped_refptr<media::AudioCapturerSource> source,
+      int sample_rate,
+      media::ChannelLayout channel_layout,
+      int frames_per_buffer,
+      bool is_remote);
 
-  explicit MediaInterfaceProvider(
-      const ConnectToApplicationCB& connect_to_app_cb);
-  ~MediaInterfaceProvider() final;
-
-  // InterfaceProvider implementation.
-  void GetInterface(const mojo::String& interface_name,
-                    mojo::ScopedMessagePipeHandle pipe) final;
+  ~ExternalMediaStreamAudioSource() final;
 
  private:
-  media::interfaces::ServiceFactory* GetMediaServiceFactory();
-  void OnConnectionError();
+  // MediaStreamAudioSource implementation.
+  bool EnsureSourceIsStarted() final;
+  void EnsureSourceIsStopped() final;
 
+  // media::AudioCapturerSource::CaptureCallback implementation.
+  void Capture(const media::AudioBus* audio_bus,
+               int audio_delay_milliseconds,
+               double volume,
+               bool key_pressed) final;
+  void OnCaptureError(const std::string& message) final;
+
+  // The external source provided to the constructor.
+  scoped_refptr<media::AudioCapturerSource> source_;
+
+  // In debug builds, check that all methods that could cause object graph
+  // or data flow changes are being called on the main thread.
   base::ThreadChecker thread_checker_;
-  ConnectToApplicationCB connect_to_app_cb_;
-  media::interfaces::ServiceFactoryPtr media_service_factory_;
 
-  DISALLOW_COPY_AND_ASSIGN(MediaInterfaceProvider);
+  // True once the source has been started successfully.
+  bool was_started_;
+
+  DISALLOW_COPY_AND_ASSIGN(ExternalMediaStreamAudioSource);
 };
 
 }  // namespace content
 
-#endif  // CONTENT_RENDERER_MEDIA_MEDIA_INTERFACE_PROVIDER_H_
+#endif  // CONTENT_RENDERER_MEDIA_EXTERNAL_MEDIA_STREAM_AUDIO_SOURCE_H_