Report if video capturing meets output protection requirement.

content/renderer/media/media_stream_video_track.cc

Index: content/renderer/media/media_stream_video_track.cc
diff --git a/content/renderer/media/media_stream_video_track.cc b/content/renderer/media/media_stream_video_track.cc
index 4a0bca04d07f8e2666ce6d7aaf10c50ac6726a7e..6f5752ada00ef62b337f7777441fe44bc816c9dd 100644
--- a/content/renderer/media/media_stream_video_track.cc
+++ b/content/renderer/media/media_stream_video_track.cc
@@ -229,7 +229,8 @@ MediaStreamVideoTrack::MediaStreamVideoTrack(
           new MediaStreamVideoTrack::FrameDeliverer(source->io_task_runner(),
                                                     enabled)),
       constraints_(constraints),
-      source_(source) {
+      source_(source),
+      video_capturing_link_secured_(true) {
   DCHECK(!constraints.isNull());
   source->AddTrack(this,
                    base::Bind(
@@ -288,4 +289,11 @@ void MediaStreamVideoTrack::OnReadyStateChanged(
     sink->OnReadyStateChanged(state);
 }
 
+void MediaStreamVideoTrack::SetVideoSinkSecured(bool is_secure) {
+  DCHECK(main_render_thread_checker_.CalledOnValidThread());
+  video_capturing_link_secured_ &= is_secure;

[miu, 2016/04/16 00:05:29]

You need to track these booleans individually.  For example, this logic fails
for this sequence:

1. Add secure sink.  Track is secure.
2. Add insecure sink.  Track is no longer secure.
3. Remove insecure sink.  Track should be secure again (because only a secure
sink remains connected).

This also needs to be fixed in the MediaStreamVideoSources.

[xjz, 2016/04/21 23:50:45]

Done.

+  if (source_)
+    source_->SetCapturingLinkSecured(video_capturing_link_secured_);
+}
+
 }  // namespace content