Move size() method to EncodedImage base class

Deleted from subclass video_coding::EncodedFrame. Also delete Length
and SetLength methods on the intermediate class
video_coding::VCMEncodedFrame.

Bug: webrtc:9378
Change-Id: I3c90b14735f622f50b2f403f79072e22fc025d11
Reviewed-on: https://webrtc-review.googlesource.com/c/112131
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25838}
diff --git a/modules/video_coding/jitter_buffer.cc b/modules/video_coding/jitter_buffer.cc
index 4a0622a..2805fbb 100644
--- a/modules/video_coding/jitter_buffer.cc
+++ b/modules/video_coding/jitter_buffer.cc
@@ -553,7 +553,7 @@
   if (retransmitted) {
     if (WaitForRetransmissions())
       jitter_estimate_.FrameNacked();
-  } else if (frame->Length() > 0) {
+  } else if (frame->size() > 0) {
     // Ignore retransmitted and empty frames.
     if (waiting_for_completion_.latest_packet_time >= 0) {
       UpdateJitterEstimate(waiting_for_completion_, true);
@@ -562,7 +562,7 @@
       UpdateJitterEstimate(*frame, false);
     } else {
       // Wait for this one to get complete.
-      waiting_for_completion_.frame_size = frame->Length();
+      waiting_for_completion_.frame_size = frame->size();
       waiting_for_completion_.latest_packet_time = frame->LatestPacketTimeMs();
       waiting_for_completion_.timestamp = frame->Timestamp();
     }
@@ -1264,7 +1264,7 @@
   // No retransmitted frames should be a part of the jitter
   // estimate.
   UpdateJitterEstimate(frame.LatestPacketTimeMs(), frame.Timestamp(),
-                       frame.Length(), incomplete_frame);
+                       frame.size(), incomplete_frame);
 }
 
 // Must be called under the critical section |crit_sect_|. Should never be