Add support for writing raw encoder output to .ivf files.

webrtc/video/vie_encoder.cc

Index: webrtc/video/vie_encoder.cc
diff --git a/webrtc/video/vie_encoder.cc b/webrtc/video/vie_encoder.cc
index 24b8ce3cd1c4e392d2a0fef1ec8ffb8f00a4050b..f587765deaf506624b2e0cffa09fa2cb36511095 100644
--- a/webrtc/video/vie_encoder.cc
+++ b/webrtc/video/vie_encoder.cc
@@ -427,6 +427,22 @@ int32_t ViEEncoder::SendData(const uint8_t payload_type,
       encoded_image.capture_time_ms_, encoded_image._buffer,
       encoded_image._length, fragmentation_header, rtp_video_hdr);
   overuse_detector_->FrameSent(encoded_image._timeStamp);
+
+  if (kEnableFrameRecording) {

[pbos-webrtc, 2016/04/05 13:31:28]

This isn't done on a known thread, for simulcast with hardware encoders you have
data races here (all hardware encoders use separate threads for callbacks).

[sprang_webrtc, 2016/04/05 16:00:53]

Ah. I'm assuming now that callbacks are at least not overlapping per simulcast
stream? Otherwise we could have reordering even before packetization?

+    int layer = rtp_video_hdr->simulcastIdx;
+    if (file_writers_[layer] == nullptr) {
+      uint64_t instance_id = reinterpret_cast<uint64_t>(this);
+      std::ostringstream oss;
+      oss << "bitstream_" << instance_id << "_" << layer << ".ivf";
+      file_writers_[layer] =
+          IvfFileWriter::Open(oss.str().c_str(), rtp_video_hdr->codec);
+    }
+    if (file_writers_[layer].get() != nullptr) {
+      bool ok = file_writers_[layer]->WriteFrame(encoded_image);
+      RTC_DCHECK(ok);
+    }
+  }
+
   return success ? 0 : -1;
 }