The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/351bb0367f7f1019c5d6aabd5682d16a0f1bec80

commit 351bb0367f7f1019c5d6aabd5682d16a0f1bec80
Author: tdresser <tdresser@chromium.org>
Date: Wed May 25 13:53:41 2016

Add touch drag UMA latency metric.

Histograms added are:
Event.Latency.QueueingTime.TouchMoveDefaultPrevented
Event.Latency.QueueingTime.TouchMoveDefaultAllowed
Event.Latency.BlockingTime.TouchMoveDefaultPrevented
Event.Latency.BlockingTime.TouchMoveDefaultAllowed

TEST=RenderWidgetHostLatencyTrackerTest.TouchBlockingAndQueueingTime
BUG= 600729 

Review-Url: https://codereview.chromium.org/1861733002
Cr-Commit-Position: refs/heads/master@{#395883}

[modify] https://crrev.com/351bb0367f7f1019c5d6aabd5682d16a0f1bec80/content/browser/renderer_host/input/render_widget_host_latency_tracker.cc
[modify] https://crrev.com/351bb0367f7f1019c5d6aabd5682d16a0f1bec80/content/browser/renderer_host/input/render_widget_host_latency_tracker.h
[modify] https://crrev.com/351bb0367f7f1019c5d6aabd5682d16a0f1bec80/content/browser/renderer_host/input/render_widget_host_latency_tracker_unittest.cc
[modify] https://crrev.com/351bb0367f7f1019c5d6aabd5682d16a0f1bec80/content/browser/renderer_host/render_widget_host_impl.cc
[modify] https://crrev.com/351bb0367f7f1019c5d6aabd5682d16a0f1bec80/tools/metrics/histograms/histograms.xml