MediaCaptureFromElement: add support for audio captureStream().

media/blink/webaudiosourceprovider_impl.h

 // Copyright 2013 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 MEDIA_BLINK_WEBAUDIOSOURCEPROVIDER_IMPL_H_
 #define MEDIA_BLINK_WEBAUDIOSOURCEPROVIDER_IMPL_H_
 
 #include <stddef.h>
 
 #include <string>
@@ skipping 51 matching lines @@
   void Pause() override;
   bool SetVolume(double volume) override;
   OutputDeviceInfo GetOutputDeviceInfo() override;
   void Initialize(const AudioParameters& params,
                   RenderCallback* renderer) override;
   void SwitchOutputDevice(const std::string& device_id,
                           const url::Origin& security_origin,
                           const OutputDeviceStatusCB& callback) override;
 
   // These methods allow a client to get a copy of the rendered audio.
-  void SetCopyAudioCallback(const CopyAudioCB& callback);
-  void ClearCopyAudioCallback();
+  virtual void SetCopyAudioCallback(const CopyAudioCB& callback);

[miu, 2016/05/13 23:40:35]

Why are these methods being made virtual?

[mcasas, 2016/05/14 02:23:47]

For MockWebAudioSourceProvider in 
html_audio_element_capturer_unittest.cc

+  virtual void ClearCopyAudioCallback();
+  base::WeakPtr<WebAudioSourceProviderImpl> AsWeakPtr() {
+    return weak_factory_.GetWeakPtr();
+  }
 
- private:
+ protected:
   friend class WebAudioSourceProviderImplTest;
   ~WebAudioSourceProviderImpl() override;
 
+ private:
   // Calls setFormat() on |client_| from the Blink renderer thread.
   void OnSetFormat();
 
   int RenderForTesting(AudioBus* audio_bus);
 
   // Used to keep the volume across reconfigurations.
   double volume_;
 
   // Tracks the current playback state.
   enum PlaybackState { kStopped, kStarted, kPlaying };
@@ skipping 15 matching lines @@
 
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<WebAudioSourceProviderImpl> weak_factory_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(WebAudioSourceProviderImpl);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BLINK_WEBAUDIOSOURCEPROVIDER_IMPL_H_