Add preemptive rate and preferred buffer size plots to event log visualizer.
Add preemptive rate and preferred buffer size plots to event log visualizer.

Bug: None
Change-Id: I185f1cd9645a850ba42cb122373d73613d118ac1
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/131128
Reviewed-by: Minyue Li <102e225d2aadac8dd4015cd04db7d6cd89bdb304@webrtc.org>
Reviewed-by: Björn Terelius <efeae16329b3cb4ac5daf80d4bfda3344c027db3@webrtc.org>
Commit-Queue: Jakob Ivarsson‎ <9ca81c2aa4aa86256fc426d7d57eed586c9fd3ac@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#27451}
TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc