Add content type extension to capabilities

webrtc/media/engine/webrtcvideoengine2.cc

Index: webrtc/media/engine/webrtcvideoengine2.cc
diff --git a/webrtc/media/engine/webrtcvideoengine2.cc b/webrtc/media/engine/webrtcvideoengine2.cc
index 087fc4e011d7a7066534e4a892238a93f0ee4be5..24135ee9216456d52f7d1529440fb1f8b0306738 100644
--- a/webrtc/media/engine/webrtcvideoengine2.cc
+++ b/webrtc/media/engine/webrtcvideoengine2.cc
@@ -49,6 +49,12 @@ bool IsFlexfecFieldTrialEnabled() {
   return webrtc::field_trial::FindFullName("WebRTC-FlexFEC-03") == "Enabled";
 }
 
+// If this field trial is enabled, we will report VideoContentType RTP extension

[brandtr, 2017/04/13 10:00:25]

But the effect of adding this extension to the capabilities means that it will
show up in the default offer SDP, and therefore by default will be sent, if
negotiated?

[ilnik, 2017/04/13 10:12:28]

Yes. I have updated the comment to be more detailed.

+// in capabilities.
+bool IsVideoContentTypeExtensionFieldTrialEnabled() {
+  return webrtc::field_trial::IsEnabled("WebRTC-VideoContentTypeExtension");
+}
+
 // Wrap cricket::WebRtcVideoEncoderFactory as a webrtc::VideoEncoderFactory.
 class EncoderFactoryAdapter : public webrtc::VideoEncoderFactory {
  public:
@@ -503,6 +509,11 @@ RtpCapabilities WebRtcVideoEngine2::GetCapabilities() const {
   capabilities.header_extensions.push_back(
       webrtc::RtpExtension(webrtc::RtpExtension::kPlayoutDelayUri,
                            webrtc::RtpExtension::kPlayoutDelayDefaultId));
+  if (IsVideoContentTypeExtensionFieldTrialEnabled()) {
+    capabilities.header_extensions.push_back(
+        webrtc::RtpExtension(webrtc::RtpExtension::kVideoContentTypeUri,
+                             webrtc::RtpExtension::kVideoContentTypeDefaultId));
+  }
   return capabilities;
 }