FrameBuffer for the new jitter buffer.

BUG=webrtc:5514
R=danilchap@webrtc.org, mflodman@webrtc.org

Review URL: https://codereview.webrtc.org/1969403007 .

Cr-Commit-Position: refs/heads/master@{#12798}

webrtc/modules/video_coding/frame_object.h

@@ -31,6 +31,7 @@ class FrameObject {
   // have to be constructed from the header data relevant to that codec.
   uint16_t picture_id;
   uint8_t spatial_layer;
+  uint32_t timestamp;
 
   size_t num_references;
   uint16_t references[kMaxFrameReferences];