client lib: Add incremental timestamps to the client library.

This patch replicates the corresponding functionality in Chrome.

This CL bring aosp/1318459 back with additional support to
disable/enable incremental timestamps.

Bug: 147863614
Change-Id: Icc5d3e2ed1e0d5c42b9e725f5e304951302e4e1e
diff --git a/CHANGELOG b/CHANGELOG
index 95516cd..bdf8b0f 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -9,6 +9,9 @@
       and async send/async recv).
   SDK:
     * Added support for writing typed proto messages inside DebugAnnotations.
+    * Added support for delta encoding of timestamps for TrackEvents.
+      To disable it, refer to `disable_incremental_timestamps` flag in
+      `track_event_config.proto`.
 
 
 v24.2 - 2022-02-10: