The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ee395f2ae50f87f43d3be2cc13b49c035d7a09f2

commit ee395f2ae50f87f43d3be2cc13b49c035d7a09f2
Author: Ria Jiang <riajiang@chromium.org>
Date: Thu Mar 01 20:24:12 2018

Collect metrics in HitTestAggregator and HitTestQuery.

Collect Event.VizHitTest.AggregateTime, Event.VizHitTest.HitTestRegions,
Event.VizHitTest.TargetTime and Event.VizHitTest.TransformTime.

Bug: 817673
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel
Change-Id: Iaae1009aa74f679a2e40c56f62e24a6fb3422be4
Reviewed-on: https://chromium-review.googlesource.com/942604
Commit-Queue: Ria Jiang <riajiang@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540270}
[modify] https://crrev.com/ee395f2ae50f87f43d3be2cc13b49c035d7a09f2/components/viz/host/hit_test/hit_test_query.cc
[modify] https://crrev.com/ee395f2ae50f87f43d3be2cc13b49c035d7a09f2/components/viz/service/hit_test/hit_test_aggregator.cc
[modify] https://crrev.com/ee395f2ae50f87f43d3be2cc13b49c035d7a09f2/tools/metrics/histograms/histograms.xml