Revert "Remove sync buffer length from FilteredCurrentDelayMs."
Revert "Remove sync buffer length from FilteredCurrentDelayMs."

This reverts commit 79890ef91faaf5d26a04083e97a3cb1218677ab0.

Reason for revert: the sync buffer was actually not counted when the buffer level filter was updated since the value was rounded down to the closest whole packet.

Original change's description:
> Remove sync buffer length from FilteredCurrentDelayMs.
> 
> The sync buffer length is already added when the buffer level filter is updated.
> 
> Bug: webrtc:10736
> Change-Id: Icbd411d4fd7b16f31b800142d1b6a8de79365d91
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/140950
> Reviewed-by: Minyue Li <minyue@webrtc.org>
> Commit-Queue: Jakob Ivarsson <9ca81c2aa4aa86256fc426d7d57eed586c9fd3ac@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#28261}

TBR=minyue@webrtc.org,9ca81c2aa4aa86256fc426d7d57eed586c9fd3ac@webrtc.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: webrtc:10736
Change-Id: Ibf4ce566484ff01421b186e03fe97fe633ba066d
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/143167
Reviewed-by: Jakob Ivarsson <9ca81c2aa4aa86256fc426d7d57eed586c9fd3ac@webrtc.org>
Commit-Queue: Jakob Ivarsson <9ca81c2aa4aa86256fc426d7d57eed586c9fd3ac@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#28335}

TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc