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..a5e6eb69940d649db5a8570563f38e96535ab74b 100644
--- a/webrtc/media/engine/webrtcvideoengine2.cc
+++ b/webrtc/media/engine/webrtcvideoengine2.cc
@@ -49,6 +49,11 @@ bool IsFlexfecFieldTrialEnabled() {
   return webrtc::field_trial::FindFullName("WebRTC-FlexFEC-03") == "Enabled";
 }
 
+bool IsVideoContentTypeExtensionEnabled() {

[brandtr, 2017/04/13 09:42:50]

Nits:

1) Add "FieldTrial" to the name of this function, so it's clear on line 511 that
this extension is gated behind a field trial.
2) Above this function, add a comment describing what happens when this field
trial is enabled.

[ilnik, 2017/04/13 09:47:44]

Done.

+  return webrtc::field_trial::FindFullName(
+             "WebRTC-VideoContentTypeExtension") == "Enabled";

[brandtr, 2017/04/13 09:42:50]

Replace with a call to this function instead:
https://cs.chromium.org/chromium/src/third_party/webrtc/system_wrappers/inclu....

Can explain offline.

[ilnik, 2017/04/13 09:47:44]

Done.

+}
+
 // Wrap cricket::WebRtcVideoEncoderFactory as a webrtc::VideoEncoderFactory.
 class EncoderFactoryAdapter : public webrtc::VideoEncoderFactory {
  public:
@@ -503,6 +508,11 @@ RtpCapabilities WebRtcVideoEngine2::GetCapabilities() const {
   capabilities.header_extensions.push_back(
       webrtc::RtpExtension(webrtc::RtpExtension::kPlayoutDelayUri,
                            webrtc::RtpExtension::kPlayoutDelayDefaultId));
+  if (IsVideoContentTypeExtensionEnabled()) {
+    capabilities.header_extensions.push_back(
+        webrtc::RtpExtension(webrtc::RtpExtension::kVideoContentTypeUri,
+                             webrtc::RtpExtension::kVideoContentTypeDefaultId));
+  }
   return capabilities;
 }