Add content type information to encoded images and corresponding rtp extension header

webrtc/media/base/fakevideocapturer.h

Index: webrtc/media/base/fakevideocapturer.h
diff --git a/webrtc/media/base/fakevideocapturer.h b/webrtc/media/base/fakevideocapturer.h
index b5bfd3496476e9e576a2c46683935ad9d9e357db..76889a4591245078b37277e058b1c71d8b0c6d06 100644
--- a/webrtc/media/base/fakevideocapturer.h
+++ b/webrtc/media/base/fakevideocapturer.h
@@ -98,10 +98,12 @@ class FakeVideoCapturer : public cricket::VideoCapturer {
           webrtc::I420Buffer::Create(adapted_width, adapted_height));
       buffer->InitializeData();
 
-      OnFrame(webrtc::VideoFrame(
-                  buffer, rotation_,
-                  next_timestamp_ / rtc::kNumNanosecsPerMicrosec),
-              width, height);
+      OnFrame(
+          webrtc::VideoFrame(buffer, rotation_,
+                             is_screencast_ ? webrtc::kVideoContent_Screenshare
+                                            : webrtc::kVideoContent_Default,
+                             next_timestamp_ / rtc::kNumNanosecsPerMicrosec),
+          width, height);
     }
     next_timestamp_ += timestamp_interval;