Add accessor methods for RTP timestamp of EncodedImage.

Intention is to make the member private, but downstream callers
must be updated to use the accessor methods first.

Bug: webrtc:9378
Change-Id: I3495bd8d545b7234fbea10abfd14f082caa420b6
Reviewed-on: https://webrtc-review.googlesource.com/82160
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24352}
diff --git a/video/send_statistics_proxy.cc b/video/send_statistics_proxy.cc
index 2fb955c..2091bad 100644
--- a/video/send_statistics_proxy.cc
+++ b/video/send_statistics_proxy.cc
@@ -250,7 +250,7 @@
   // Check for jump in timestamp.
   if (!encoded_frames_.empty()) {
     uint32_t oldest_timestamp = encoded_frames_.begin()->first;
-    if (ForwardDiff(oldest_timestamp, encoded_frame._timeStamp) >
+    if (ForwardDiff(oldest_timestamp, encoded_frame.Timestamp()) >
         kMaxEncodedFrameTimestampDiff) {
       // Gap detected, clear frames to have a sequence where newest timestamp
       // is not too far away from oldest in order to distinguish old and new.
@@ -262,7 +262,7 @@
   if (it == encoded_frames_.end()) {
     // First frame with this timestamp.
     encoded_frames_.insert(
-        std::make_pair(encoded_frame._timeStamp,
+        std::make_pair(encoded_frame.Timestamp(),
                        Frame(now_ms, encoded_frame._encodedWidth,
                              encoded_frame._encodedHeight, simulcast_idx)));
     sent_fps_counter_.Add(1);