MediaCaptureFromElement: add support for audio captureStream().

media/blink/webaudiosourceprovider_impl.h

Index: media/blink/webaudiosourceprovider_impl.h
diff --git a/media/blink/webaudiosourceprovider_impl.h b/media/blink/webaudiosourceprovider_impl.h
index 6bf3b0aa9e379b9811e06598a53c97186fb74b47..6ed677931595d082db0744e14e244c086576ed41 100644
--- a/media/blink/webaudiosourceprovider_impl.h
+++ b/media/blink/webaudiosourceprovider_impl.h
@@ -72,6 +72,12 @@ class MEDIA_BLINK_EXPORT WebAudioSourceProviderImpl
   void SetCopyAudioCallback(const CopyAudioCB& callback);
   void ClearCopyAudioCallback();
 
+  base::WeakPtr<WebAudioSourceProviderImpl> AsWeakPtr() {
+    return weak_factory_.GetWeakPtr();
+  }
+
+  int RenderForTesting(AudioBus* audio_bus);

[miu, 2016/05/19 22:44:30]

Not sure you should have made this public. Instead, could your test code just
call provideInput()?

[mcasas, 2016/05/19 23:57:55]

provideInput() is only available for the render-to-WebAudio
path: WASPImpl can only pass audio onwards to either
|renderer_| or |client_|, but not both. provideAudio() is 
used by the second path (hence the check in [1]). I could
modify the unittests to use this particular path, but IMHO
is not worth it. (Also I can't easily make me friend of this
class because HTMLAudioElementCapturerSourceTest is
in content/, argh!).

[1]
https://code.google.com/p/chromium/codesearch#chromium/src/media/blink/webaud...

+
  private:
   friend class WebAudioSourceProviderImplTest;
   ~WebAudioSourceProviderImpl() override;
@@ -79,8 +85,6 @@ class MEDIA_BLINK_EXPORT WebAudioSourceProviderImpl
   // 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_;