The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/51eb7a0298cf225fc41e774b7aaa4a87f34d72f2

commit 51eb7a0298cf225fc41e774b7aaa4a87f34d72f2
Author: Brian White <bcwhite@chromium.org>
Date: Thu Nov 01 15:59:32 2018

Add history-table aggregation to UKM config.

Bug:  900230 
Change-Id: I37dd02c2a7e1b8ef586e101e036d6871c7361424
Reviewed-on: https://chromium-review.googlesource.com/c/1307935
Reviewed-by: Bryan McQuade <bmcquade@chromium.org>
Commit-Queue: Brian White <bcwhite@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604599}
[modify] https://crrev.com/51eb7a0298cf225fc41e774b7aaa4a87f34d72f2/tools/metrics/ukm/ukm.xml
[modify] https://crrev.com/51eb7a0298cf225fc41e774b7aaa4a87f34d72f2/tools/metrics/ukm/ukm_model.py

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bd82085c20cc94295f9e5e59d65a6e1d0c262922

commit bd82085c20cc94295f9e5e59d65a6e1d0c262922
Author: Brian White <bcwhite@chromium.org>
Date: Fri Nov 02 19:19:28 2018

Remove enumeration aggregations from ukm.xml file.

Until https://critique.corp.google.com/#review/206234268 is submitted,
enumerations cannot be configured because their proportion values will
change significantly with that chnage.

Bug:  900230 
Change-Id: I1670dabf72e4a2d6d00dd1c295961571b61fe9fa
Reviewed-on: https://chromium-review.googlesource.com/c/1313189
Reviewed-by: Bryan McQuade <bmcquade@chromium.org>
Commit-Queue: Brian White <bcwhite@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605009}
[modify] https://crrev.com/bd82085c20cc94295f9e5e59d65a6e1d0c262922/tools/metrics/ukm/ukm.xml