MediaCaptureFromElement: add support for audio captureStream().

content/renderer/renderer_blink_platform_impl.cc

Index: content/renderer/renderer_blink_platform_impl.cc
diff --git a/content/renderer/renderer_blink_platform_impl.cc b/content/renderer/renderer_blink_platform_impl.cc
index 94976ac52f2a57a92ceb311547d8540f04d3a0f1..7cbdeaaa8805b86e3614a3b3d7b4ce0bae6d0f18 100644
--- a/content/renderer/renderer_blink_platform_impl.cc
+++ b/content/renderer/renderer_blink_platform_impl.cc
@@ -8,6 +8,7 @@
 
 #include "base/command_line.h"
 #include "base/files/file_path.h"
+#include "base/guid.h"

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

Is this new #include still needed?

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

Yes, for l.988
const WebString track_id = WebString::fromUTF8(base::GenerateGUID());

 #include "base/lazy_instance.h"
 #include "base/location.h"
 #include "base/logging.h"
@@ -61,6 +62,7 @@
 #include "content/renderer/gamepad_shared_memory_reader.h"
 #include "content/renderer/media/audio_decoder.h"
 #include "content/renderer/media/canvas_capture_handler.h"
+#include "content/renderer/media/html_audio_element_capturer_source.h"
 #include "content/renderer/media/html_video_element_capturer_source.h"
 #include "content/renderer/media/image_capture_frame_grabber.h"
 #include "content/renderer/media/media_recorder_handler.h"
@@ -975,6 +977,33 @@ void RendererBlinkPlatformImpl::createHTMLVideoElementCapturer(
 #endif
 }
 
+void RendererBlinkPlatformImpl::createHTMLAudioElementCapturer(
+    WebMediaStream* web_media_stream,
+    WebMediaPlayer* web_media_player) {
+  DCHECK(web_media_stream);
+  DCHECK(web_media_player);
+
+  blink::WebMediaStreamSource web_media_stream_source;
+  blink::WebMediaStreamTrack web_media_stream_track;
+  const WebString track_id = WebString::fromUTF8(base::GenerateGUID());
+
+  web_media_stream_source.initialize(track_id,
+                                     blink::WebMediaStreamSource::TypeAudio,
+                                     track_id,
+                                     false /* is_remote */);
+  web_media_stream_track.initialize(web_media_stream_source);
+
+  MediaStreamAudioSource* const media_stream_source =
+      HtmlAudioElementCapturerSource::CreateFromWebMediaPlayerImpl(
+          web_media_player);
+
+  // Takes ownership of|media_stream_source|.
+  web_media_stream_source.setExtraData(media_stream_source);
+
+  if (media_stream_source->ConnectToTrack(web_media_stream_track))
+    web_media_stream->addTrack(web_media_stream_track);

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

I'm not sure, but I think you *might* want to unconditionally add the track to
the web_media_stream even if ConnectToTrack() returns false. The reason is that
ConnectToTrack() will return false if the source couldn't be started, but it
will also still create a MediaStreamAudioTrack and call
web_media_stream_track.setExtraData(media_stream_audio_track). In this case, a
MediaStreamTrack will be presented to the user JavaScript in the "ended" state.

So, when the source cannot be started, do you want the user's JavaScript to see:
1) an "ended" track added to the MediaStream?  Or, 2) no audio track added to
the MediaStream?  I suspect #1 would be more robust (and consistent with the
other MediaStream specs).

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

Makes sense, done.

+}
+
 //------------------------------------------------------------------------------
 
 WebImageCaptureFrameGrabber*