Revert "Remove RTPVideoHeader::h264() accessors."

This reverts commit dfbced6504720d2c0807d7b92798eb80ba3f8be9.

Reason for revert: Crashes when making a video call.

#9	0x00000001043dd8d8 in webrtc::RTPVideoHeaderH264& absl::variant_internal::TypedThrowBadVariantAccess<webrtc::RTPVideoHeaderH264&>() at /third_party/absl/types/internal/variant.h:315
#10	0x00000001043dd8ac in absl::variant_internal::VariantAccessResultImpl<2ul, absl::variant<webrtc::RTPVideoHeaderVP8, webrtc::RTPVideoHeaderVP9, webrtc::RTPVideoHeaderH264>&&&>::type absl::variant_internal::VariantCoreAccess::CheckedAccess<2ul, absl::variant<webrtc::RTPVideoHeaderVP8, webrtc::RTPVideoHeaderVP9, webrtc::RTPVideoHeaderH264>&>(absl::variant<webrtc::RTPVideoHeaderVP8, webrtc::RTPVideoHeaderVP9, webrtc::RTPVideoHeaderH264>&&&) at /third_party/absl/types/internal/variant.h:597
#11	0x00000001043db778 in webrtc::RTPVideoHeaderH264& absl::get<webrtc::RTPVideoHeaderH264, webrtc::RTPVideoHeaderVP8, webrtc::RTPVideoHeaderVP9, webrtc::RTPVideoHeaderH264>(absl::variant<webrtc::RTPVideoHeaderVP8, webrtc::RTPVideoHeaderVP9, webrtc::RTPVideoHeaderH264>&) at /third_party/absl/types/variant.h:299
#12	0x0000000104558bcc in webrtc::RtpPacketizer::Create(webrtc::VideoCodecType, unsigned long, unsigned long, webrtc::RTPVideoHeader const*, webrtc::FrameType) at webrtc/modules/rtp_rtcp/source/rtp_format.cc:30

Original change's description:
> Remove RTPVideoHeader::h264() accessors.
>
> Bug: none
> Change-Id: I043bcaf358575688b223bc3631506e148b47fd58
> Reviewed-on: https://webrtc-review.googlesource.com/88220
> Reviewed-by: Stefan Holmer <stefan@webrtc.org>
> Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
> Commit-Queue: Philip Eliasson <philipel@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#23971}

TBR=danilchap@webrtc.org,stefan@webrtc.org,philipel@webrtc.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: none
Change-Id: If99bcabdfe3cae7094f24e407bbe2f47233e46e3
Reviewed-on: https://webrtc-review.googlesource.com/88820
Commit-Queue: JT Teh <jtteh@webrtc.org>
Reviewed-by: Zeke Chin <tkchin@webrtc.org>
Reviewed-by: JT Teh <jtteh@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23993}
diff --git a/modules/video_coding/video_packet_buffer_unittest.cc b/modules/video_coding/video_packet_buffer_unittest.cc
index f588026..58611ff 100644
--- a/modules/video_coding/video_packet_buffer_unittest.cc
+++ b/modules/video_coding/video_packet_buffer_unittest.cc
@@ -508,19 +508,17 @@
                   uint8_t* data = nullptr) {  // data pointer
     VCMPacket packet;
     packet.codec = kVideoCodecH264;
-    auto& h264_header =
-        packet.video_header.video_type_header.emplace<RTPVideoHeaderH264>();
     packet.seqNum = seq_num;
     packet.timestamp = timestamp;
     if (keyframe == kKeyFrame) {
       if (sps_pps_idr_is_keyframe_) {
-        h264_header.nalus[0].type = H264::NaluType::kSps;
-        h264_header.nalus[1].type = H264::NaluType::kPps;
-        h264_header.nalus[2].type = H264::NaluType::kIdr;
-        h264_header.nalus_length = 3;
+        packet.video_header.h264().nalus[0].type = H264::NaluType::kSps;
+        packet.video_header.h264().nalus[1].type = H264::NaluType::kPps;
+        packet.video_header.h264().nalus[2].type = H264::NaluType::kIdr;
+        packet.video_header.h264().nalus_length = 3;
       } else {
-        h264_header.nalus[0].type = H264::NaluType::kIdr;
-        h264_header.nalus_length = 1;
+        packet.video_header.h264().nalus[0].type = H264::NaluType::kIdr;
+        packet.video_header.h264().nalus_length = 1;
       }
     }
     packet.is_first_packet_in_frame = first == kFirst;
@@ -594,14 +592,12 @@
       new uint8_t[sizeof(data_data) + EncodedImage::kBufferPaddingBytesH264]);
 
   VCMPacket packet;
-  auto& h264_header =
-      packet.video_header.video_type_header.emplace<RTPVideoHeaderH264>();
-  h264_header.nalus_length = 1;
-  h264_header.nalus[0].type = H264::NaluType::kIdr;
-  h264_header.packetization_type = kH264SingleNalu;
+  packet.video_header.h264().nalus_length = 1;
+  packet.video_header.h264().nalus[0].type = H264::NaluType::kIdr;
   packet.seqNum = seq_num;
   packet.codec = kVideoCodecH264;
   packet.insertStartCode = true;
+  packet.video_header.h264().packetization_type = kH264SingleNalu;
   packet.dataPtr = data;
   packet.sizeBytes = sizeof(data_data);
   packet.is_first_packet_in_frame = true;
@@ -759,9 +755,7 @@
   EXPECT_TRUE(packet_buffer_->InsertPacket(&packet));
 
   packet.codec = kVideoCodecH264;
-  auto& h264_header =
-      packet.video_header.video_type_header.emplace<RTPVideoHeaderH264>();
-  h264_header.nalus_length = 1;
+  packet.video_header.h264().nalus_length = 1;
   packet.timestamp = 3;
   packet.seqNum = 3;
   EXPECT_TRUE(packet_buffer_->InsertPacket(&packet));
@@ -784,9 +778,7 @@
   packet.frameType = kVideoFrameKey;
   packet.is_first_packet_in_frame = true;
   packet.markerBit = true;
-  auto& h264_header =
-      packet.video_header.video_type_header.emplace<RTPVideoHeaderH264>();
-  h264_header.nalus_length = kMaxNalusPerPacket;
+  packet.video_header.h264().nalus_length = kMaxNalusPerPacket;
   packet.sizeBytes = 0;
   packet.dataPtr = nullptr;
   EXPECT_TRUE(packet_buffer_->InsertPacket(&packet));
@@ -881,10 +873,9 @@
 };
 
 TEST_F(TestPacketBufferH264IdrIsKeyframe, IdrIsKeyframe) {
-  auto& h264_header =
-      packet_.video_header.video_type_header.emplace<RTPVideoHeaderH264>();
-  h264_header.nalus[0].type = H264::NaluType::kIdr;
-  h264_header.nalus_length = 1;
+  packet_.video_header.h264().nalus[0].type = H264::NaluType::kIdr;
+  packet_.video_header.h264().nalus_length = 1;
+
   packet_buffer_->InsertPacket(&packet_);
 
   ASSERT_EQ(1u, frames_from_callback_.size());
@@ -892,12 +883,10 @@
 }
 
 TEST_F(TestPacketBufferH264IdrIsKeyframe, SpsPpsIdrIsKeyframe) {
-  auto& h264_header =
-      packet_.video_header.video_type_header.emplace<RTPVideoHeaderH264>();
-  h264_header.nalus[0].type = H264::NaluType::kSps;
-  h264_header.nalus[1].type = H264::NaluType::kPps;
-  h264_header.nalus[2].type = H264::NaluType::kIdr;
-  h264_header.nalus_length = 3;
+  packet_.video_header.h264().nalus[0].type = H264::NaluType::kSps;
+  packet_.video_header.h264().nalus[1].type = H264::NaluType::kPps;
+  packet_.video_header.h264().nalus[2].type = H264::NaluType::kIdr;
+  packet_.video_header.h264().nalus_length = 3;
 
   packet_buffer_->InsertPacket(&packet_);
 
@@ -913,10 +902,8 @@
 };
 
 TEST_F(TestPacketBufferH264SpsPpsIdrIsKeyframe, IdrIsNotKeyframe) {
-  auto& h264_header =
-      packet_.video_header.video_type_header.emplace<RTPVideoHeaderH264>();
-  h264_header.nalus[0].type = H264::NaluType::kIdr;
-  h264_header.nalus_length = 1;
+  packet_.video_header.h264().nalus[0].type = H264::NaluType::kIdr;
+  packet_.video_header.h264().nalus_length = 1;
 
   packet_buffer_->InsertPacket(&packet_);
 
@@ -925,11 +912,9 @@
 }
 
 TEST_F(TestPacketBufferH264SpsPpsIdrIsKeyframe, SpsPpsIsNotKeyframe) {
-  auto& h264_header =
-      packet_.video_header.video_type_header.emplace<RTPVideoHeaderH264>();
-  h264_header.nalus[0].type = H264::NaluType::kSps;
-  h264_header.nalus[1].type = H264::NaluType::kPps;
-  h264_header.nalus_length = 2;
+  packet_.video_header.h264().nalus[0].type = H264::NaluType::kSps;
+  packet_.video_header.h264().nalus[1].type = H264::NaluType::kPps;
+  packet_.video_header.h264().nalus_length = 2;
 
   packet_buffer_->InsertPacket(&packet_);
 
@@ -938,12 +923,10 @@
 }
 
 TEST_F(TestPacketBufferH264SpsPpsIdrIsKeyframe, SpsPpsIdrIsKeyframe) {
-  auto& h264_header =
-      packet_.video_header.video_type_header.emplace<RTPVideoHeaderH264>();
-  h264_header.nalus[0].type = H264::NaluType::kSps;
-  h264_header.nalus[1].type = H264::NaluType::kPps;
-  h264_header.nalus[2].type = H264::NaluType::kIdr;
-  h264_header.nalus_length = 3;
+  packet_.video_header.h264().nalus[0].type = H264::NaluType::kSps;
+  packet_.video_header.h264().nalus[1].type = H264::NaluType::kPps;
+  packet_.video_header.h264().nalus[2].type = H264::NaluType::kIdr;
+  packet_.video_header.h264().nalus_length = 3;
 
   packet_buffer_->InsertPacket(&packet_);