Move rtp_timestamp_to_frame_num_ map from VideoProcessor to Stats class.

Let Stats class handle rtp timestamp to frame number mapping.

Bug: none
Change-Id: I2a29c89a25c75c4bbd6c6368a5d10514f90b3c42
Reviewed-on: https://webrtc-review.googlesource.com/41220
Commit-Queue: Åsa Persson <asapersson@webrtc.org>
Reviewed-by: Sergey Silkin <ssilkin@webrtc.org>
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21709}

modules/video_coding/codecs/test/videoprocessor.h

@@ -218,11 +218,6 @@ class VideoProcessor {
   size_t num_encoded_frames_ RTC_GUARDED_BY(sequence_checker_);
   size_t num_decoded_frames_ RTC_GUARDED_BY(sequence_checker_);
 
-  // Store an RTP timestamp -> frame number map, since the timestamps are
-  // based off of the frame rate, which can change mid-test.
-  std::map<size_t, size_t> rtp_timestamp_to_frame_num_
-      RTC_GUARDED_BY(sequence_checker_);
-
   // Keep track of if we have excluded the first key frame from packet loss.
   bool first_key_frame_has_been_excluded_ RTC_GUARDED_BY(sequence_checker_);