Revert "Perfetto: Stop splitting _COMPLETE events"

This reverts commit 53e8b2a294d66219b5c4daf00dda1cb9f822a54f.

Reason for revert: crbug.com/910704

Original change's description:
> Perfetto: Stop splitting _COMPLETE events
> 
> The current Perfetto backend splits _COMPLETE trace events into
> separate _BEGIN and _END pairs, as it's not very feasible to modify
> existing events after they're written into the Shared Memory Buffers.
> 
> This is causing some issues with the trace-viewer which has some
> assumptions about the ordering of begin/end events vs. async events,
> and is also bloating the sizes of traces and adding extra
> overhead for the perf infra.
> 
> Instead, we now keep the _COMPLETE events in an internal stack in
> TLS and only emit them when we have their duration.
> 
> R=​eseckler@chromium.org,skyostil@chromium.org
> 
> Bug: 909728,888558
> Change-Id: I80e37264de66d8bbcb6c9095d21047957fd6eb9f
> Reviewed-on: https://chromium-review.googlesource.com/c/1354503
> Commit-Queue: oysteine <oysteine@chromium.org>
> Reviewed-by: Eric Seckler <eseckler@chromium.org>
> Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#612360}

TBR=oysteine@chromium.org,skyostil@chromium.org,eseckler@chromium.org

Change-Id: I0cda9ab36248042c3889d810bfd07a6d03a6d58e
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 909728, 888558
Reviewed-on: https://chromium-review.googlesource.com/c/1357500
Reviewed-by: oysteine <oysteine@chromium.org>
Commit-Queue: oysteine <oysteine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612776}
6 files changed