Revert of Protect new header extension by field trial experiment to allow hardcoding it in SDP

webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc b/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc
index 129cee5ca9b8f8a7be723d40b4543e8a1012e9f1..3f4c401a19d5c43ff9f64c6a9e3bd14d60ff9fb6 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc
@@ -28,7 +28,7 @@
 #include "webrtc/modules/rtp_rtcp/source/rtp_format_vp9.h"
 #include "webrtc/modules/rtp_rtcp/source/rtp_header_extensions.h"
 #include "webrtc/modules/rtp_rtcp/source/rtp_packet_to_send.h"
-#include "webrtc/system_wrappers/include/field_trial.h"
+
 namespace webrtc {
 
 namespace {
@@ -328,8 +328,7 @@
       last_rotation_ = current_rotation;
       // Report content type only for key frames.
       if (frame_type == kVideoFrameKey &&
-          video_header->content_type != VideoContentType::UNSPECIFIED &&
-          webrtc::field_trial::IsEnabled("WebRTC-VideoContentTypeExtension")) {
+          video_header->content_type != VideoContentType::UNSPECIFIED) {
         last_packet->SetExtension<VideoContentTypeExtension>(
             video_header->content_type);
       }