Remove RTPVideoHeader::vp9() accessors.

TBR=stefan@webrtc.org

Bug: none
Change-Id: Ia2f728ea3377754a16a0b081e25c4479fe211b3e
Reviewed-on: https://webrtc-review.googlesource.com/93024
Commit-Queue: Philip Eliasson <philipel@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24243}
diff --git a/video/picture_id_tests.cc b/video/picture_id_tests.cc
index 0da5d0a..3c43d7d 100644
--- a/video/picture_id_tests.cc
+++ b/video/picture_id_tests.cc
@@ -101,11 +101,14 @@
         parsed->tl0_pic_idx = parsed_payload.video_header().vp8().tl0PicIdx;
         parsed->temporal_idx = parsed_payload.video_header().vp8().temporalIdx;
         break;
-      case kVideoCodecVP9:
-        parsed->picture_id = parsed_payload.video_header().vp9().picture_id;
-        parsed->tl0_pic_idx = parsed_payload.video_header().vp9().tl0_pic_idx;
-        parsed->temporal_idx = parsed_payload.video_header().vp9().temporal_idx;
+      case kVideoCodecVP9: {
+        const auto& vp9_header = absl::get<RTPVideoHeaderVP9>(
+            parsed_payload.video_header().video_type_header);
+        parsed->picture_id = vp9_header.picture_id;
+        parsed->tl0_pic_idx = vp9_header.tl0_pic_idx;
+        parsed->temporal_idx = vp9_header.temporal_idx;
         break;
+      }
       default:
         RTC_NOTREACHED();
         break;