moving this to hjd. we were discussing this recently and he is reshuffling the OS dumping code as we speak, and very soon (weeks?) will be able to emit that as part of the trace.
the only other action left then would be adding that number to the metric, but that is like a 2-3 liner and perezju@ can take care of that once we have the data in the trace.

CL out for review here: https://codereview.chromium.org/3012213002/

Juan, do you know if we need to do something to make this appear on the dashboard (other than creating the TBMv2 metric in tracing) or does it just work(TM)?

it just work(TM)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/67e58ded7ed5c2ca1e60a507d4f9d92c705c63bb

commit 67e58ded7ed5c2ca1e60a507d4f9d92c705c63bb
Author: catapult-deps-roller@chromium.org <catapult-deps-roller@chromium.org>
Date: Tue Sep 12 20:38:22 2017

Roll src/third_party/catapult/ 000134387..7370e9da6 (4 commits)

https://chromium.googlesource.com/external/github.com/catapult-project/catapult.git/+log/000134387797..7370e9da6e0c

$ git log 000134387..7370e9da6 --date=short --no-merges --format='%ad %ae %s'
2017-09-12 benjhayden Document diagnostics required by dashboard.
2017-09-12 hjd tracing: Add private footprint
2017-09-12 loloangela Fix errors related to invalid-name pt. 6
2017-09-12 stephen.kyle tracing: include start,end events in loading_metric's other timeTo metrics

Created with:
  roll-dep src/third_party/catapult
BUG= 737325 


Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, see:
http://www.chromium.org/developers/tree-sheriffs/sheriff-details-chromium#TOC-Failures-due-to-DEPS-rolls


CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_optional_gpu_tests_rel
TBR=sullivan@chromium.org

Change-Id: Ie0aed1db0d86824075dafd9cf7958f68be979999
Reviewed-on: https://chromium-review.googlesource.com/663613
Reviewed-by: <catapult-deps-roller@chromium.org>
Commit-Queue: <catapult-deps-roller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501384}
[modify] https://crrev.com/67e58ded7ed5c2ca1e60a507d4f9d92c705c63bb/DEPS

Yup, there is nothing else to do. Metric is already starting to flow through the dashboards:
https://chromeperf.appspot.com/report?sid=657be4bbc6a3c6a7d469c579e55bbee5c371fb7ecd5335d433038bc933cfd44d