Cast: Basic cast_receiver API for chrome.

content/public/renderer/media_stream_source_api.cc

+// Copyright 2015 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.
+
+#include "content/public/renderer/media_stream_source_api.h"
+
+#include "base/callback.h"
+#include "base/strings/utf_string_conversions.h"
+#include "content/renderer/media/media_stream_audio_source.h"
+#include "content/renderer/media/media_stream_video_capturer_source.h"
+#include "media/base/audio_capturer_source.h"
+#include "media/base/video_capturer_source.h"
+#include "third_party/WebKit/public/platform/WebMediaDeviceInfo.h"
+#include "third_party/WebKit/public/platform/WebMediaStreamSource.h"
+
+namespace content {
+
+void InitializeVideoWebMediaStreamSource(
+    scoped_refptr<media::VideoCapturerSource> source,
+    blink::WebMediaStreamSource* webkit_source) {
+  webkit_source->initialize(base::UTF8ToUTF16(""),
+                            blink::WebMediaStreamSource::TypeVideo,
+                            base::UTF8ToUTF16(""),
+                            true /* remote */,

[perkj_chrome, 2015/02/09 14:50:27]

Remote means that this is something you receive.
read_only means that the source  can not be changed by constraints.

http://w3c.github.io/mediacapture-main/getusermedia.html#widl-MediaStreamTrac...

(these are not exposed to JS (yet))

If this API is only intended for those use cases it should be documented in the
header file.

[hubbe, 2015/02/09 20:13:32]

I've added and documented these arguments to the API methods.

+                            true /* readonly */);
+  webkit_source->setExtraData(
+      new content::MediaStreamVideoCapturerSource(

[perkj_chrome, 2015/02/09 14:50:27]

We had a few discussion regarding inheritance and delegation when we started
refactoring MediaStreamSources.
MediaStreamVideoSource is the base class and the class I would have expected you
to inherit and use for video. There are a few different other video specific
ones already such as the one from video tracks received from a PeerConnection.
But I like delegation and I like this. 

[hubbe, 2015/02/09 20:13:32]

I started out with trying to do this, but MediaStreamVideoSource is not an
interface and putting it in content/public would either require some major
refactoring, or moving a lot of stuff into content/public.

When I found the AudioCapturerSource class, I realized I could replicate this
pattern for video, which would be a much cleaner way to do things
implementation-wise. (However, it does tend to mess up some terminology and
assumptions about what is local and what isn't...)

+          StreamDeviceInfo(),

[perkj_chrome, 2015/02/09 14:50:27]

Humm, StreamDeviceInfo seems wrong here. Its only used by video cameras and tab
capture / screen capture. I wonder if it can be removed all together from
MediaStreamSource now. (I don't expect you to do it)

Note though that if you had choosen to implement MediaStreamVideoSource instead,
you would not have needed to use specify it even though it still exist in
MediaStreamSource. 

Can you move them from the ctor to another public method so you don't have to
provide them?

[hubbe, 2015/02/09 20:13:32]

Fixed the constructor to not require the device info and update all call sites.

+          content::MediaStreamSource::SourceStoppedCallback(),
+          source));
+}
+
+void InitializeAudioWebMediaStreamSource(
+    scoped_refptr<media::AudioCapturerSource> source,
+    blink::WebMediaStreamSource* webkit_source) {
+  webkit_source->initialize(base::UTF8ToUTF16(""),
+                            blink::WebMediaStreamSource::TypeAudio,
+                            base::UTF8ToUTF16(""),
+                            true /* remote */,
+                            true /* readonly */);
+  MediaStreamAudioSource* audio_source(
+        new MediaStreamAudioSource(
+            -1,
+            StreamDeviceInfo(),
+            content::MediaStreamSource::SourceStoppedCallback(),
+            RenderThreadImpl::current()->GetPeerConnectionDependencyFactory()));
+  scoped_refptr<WebRtcAudioCapturer> capturer(
+      WebRtcAudioCapturer::CreateCapturer(
+            -1,

[perkj_chrome, 2015/02/09 14:50:27]

indentation

[hubbe, 2015/02/09 20:13:32]

Done.

+            StreamDeviceInfo(),
+            blink::WebMediaConstraints(),
+            NULL,
+            audio_source));
+  media::AudioParameters params;
+  capturer->SetCapturerSource(source, params);
+  audio_source->SetAudioCapturer(capturer);
+  webkit_source->setExtraData(audio_source);
+}
+
+}  // namespace content