Replace SequencedTaskChecker in RTPSenderVideo

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 916561ea876bbc40af46433dca401e7a5519f6b7..af369ba7add4d23ff205bd389a6ec7374ed81162 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc
@@ -55,9 +55,7 @@ RTPSenderVideo::RTPSenderVideo(Clock* clock, RTPSender* rtp_sender)
       delta_fec_params_{0, 1, kFecMaskRandom},
       key_fec_params_{0, 1, kFecMaskRandom},
       fec_bitrate_(1000, RateStatistics::kBpsScale),
-      video_bitrate_(1000, RateStatistics::kBpsScale) {
-  encoder_checker_.Detach();
-}
+      video_bitrate_(1000, RateStatistics::kBpsScale) { }
 
 RTPSenderVideo::~RTPSenderVideo() {}
 
@@ -245,7 +243,6 @@ bool RTPSenderVideo::SendVideo(RtpVideoCodecTypes video_type,
                                size_t payload_size,
                                const RTPFragmentationHeader* fragmentation,
                                const RTPVideoHeader* video_header) {
-  RTC_DCHECK_CALLED_SEQUENTIALLY(&encoder_checker_);
   if (payload_size == 0)
     return false;
 
@@ -267,6 +264,7 @@ bool RTPSenderVideo::SendVideo(RtpVideoCodecTypes video_type,
   if (video_header) {
     // Set rotation when key frame or when changed (to follow standard).
     // Or when different from 0 (to follow current receiver implementation).
+    rtc::CritScope cs(&crit_);

[magjed_webrtc, 2016/11/10 10:04:03]

Can you easily merge this crit scope with the other crit scope in this function?
From a quick glance, it looks safe to move that crit scope up here.

[danilchap, 2016/11/10 10:14:53]

no, it is not that easy unfortunately:
extensions need to be set for accurate calculate of max_data_payload_length,
that one required for packetizer.

It should be easier to merge this lock with hidden lock in FecPacketOverhead
function though.

[danilchap, 2016/11/10 10:17:32]

on a second though I'm wrong, it is not hard: just remember
retransmission_settings_ inside a lock,

packetizer->GetStorateType can be called outside lock after that.

[kthelgason, 2016/11/10 10:38:26]

Is there a good reason to not just lock during the whole function scope?

[danilchap, 2016/11/10 10:56:44]

It is too dangerous:
SendVideoPacket* functions may call transport function internally, you
definitely want to exclude that.

calls to rtp_sender have own locks, creating lock dependencies i.e. increasing
chance of deadlock.

creating packetizer may be can be under lock, but since it is not hard to avoid
that, better to.


May it is ok to land as it is and solve 'too many locks' problem in a different
CL.

     VideoRotation current_rotation = video_header->rotation;
     if (frame_type == kVideoFrameKey || current_rotation != last_rotation_ ||
         current_rotation != kVideoRotation_0)