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

webrtc/modules/video_coding/generic_decoder.cc

Index: webrtc/modules/video_coding/generic_decoder.cc
diff --git a/webrtc/modules/video_coding/generic_decoder.cc b/webrtc/modules/video_coding/generic_decoder.cc
index 2121ab63067acdafe71e7f1cb7ceaf90c3b1196d..f5d9cfe07396ab03d9767a6ec6ac0fa38ed6c1dc 100644
--- a/webrtc/modules/video_coding/generic_decoder.cc
+++ b/webrtc/modules/video_coding/generic_decoder.cc
@@ -87,7 +87,7 @@
   decodedImage.set_timestamp_us(
       frameInfo->renderTimeMs * rtc::kNumMicrosecsPerMillisec);
   decodedImage.set_rotation(frameInfo->rotation);
-  _receiveCallback->FrameToRender(decodedImage, qp);
+  _receiveCallback->FrameToRender(decodedImage, qp, frameInfo->content_type);
 }
 
 int32_t VCMDecodedFrameCallback::ReceivedDecodedReferenceFrame(
@@ -131,7 +131,8 @@
       _decoder(decoder),
       _codecType(kVideoCodecUnknown),
       _isExternal(isExternal),
-      _keyFrameDecoded(false) {}
+      _keyFrameDecoded(false),
+      _last_keyframe_content_type(VideoContentType::UNSPECIFIED) {}
 
 VCMGenericDecoder::~VCMGenericDecoder() {}
 
@@ -149,6 +150,15 @@
     _frameInfos[_nextFrameInfoIdx].decodeStartTimeMs = nowMs;
     _frameInfos[_nextFrameInfoIdx].renderTimeMs = frame.RenderTimeMs();
     _frameInfos[_nextFrameInfoIdx].rotation = frame.rotation();
+    // Set correctly only for key frames. Thus, use latest key frame
+    // content type. If the corresponding key frame was lost, decode will fail
+    // and content type will be ignored.
+    if (frame.FrameType() == kVideoFrameKey) {
+      _frameInfos[_nextFrameInfoIdx].content_type = frame.contentType();
+      _last_keyframe_content_type = frame.contentType();
+    } else {
+      _frameInfos[_nextFrameInfoIdx].content_type = _last_keyframe_content_type;
+    }
     _callback->Map(frame.TimeStamp(), &_frameInfos[_nextFrameInfoIdx]);
 
     _nextFrameInfoIdx = (_nextFrameInfoIdx + 1) % kDecoderFrameMemoryLength;