measure decode time in TimeDelta instead of ms

increasing precision since summing up rounded values leads to
a rounding error, in particular for small frames which take very
little time to decode.

BUG=webrtc:12526,webrtc:13756

Change-Id: I647c702808856a002c746ed9f115aa9bcaddc1f3
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/262810
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Philipp Hancke <philipp.hancke@googlemail.com>
Cr-Commit-Position: refs/heads/main@{#37249}
diff --git a/video/video_stream_decoder2.h b/video/video_stream_decoder2.h
index a301d32..995008d 100644
--- a/video/video_stream_decoder2.h
+++ b/video/video_stream_decoder2.h
@@ -41,7 +41,7 @@
   // Implements VCMReceiveCallback.
   int32_t FrameToRender(VideoFrame& video_frame,
                         absl::optional<uint8_t> qp,
-                        int32_t decode_time_ms,
+                        TimeDelta decode_time,
                         VideoContentType content_type) override;
   void OnDroppedFrames(uint32_t frames_dropped) override;
   void OnIncomingPayloadType(int payload_type) override;