Please explain what this means in more detail.

There are couple of minor issues in how data usage is recorded using Android traffic stats API:
(i) |rx_bytes_os_| and |tx_bytes_os_| are not initialized in the constructor. This means we are losing some of the data.
(ii) Lot of samples in the DataUse.Bytes.*.OS histograms have 0-value.

This should be a quick fix.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e10fdac86b82f2e64a63815a9e08789582e6c8f9

commit e10fdac86b82f2e64a63815a9e08789582e6c8f9
Author: tbansal <tbansal@chromium.org>
Date: Wed Feb 22 23:50:27 2017

DataUse: Initialize byte counts using Android TrafficStats.

Also, a minor optimization to not record 0-value samples in the
histograms.

BUG= 692737 

Review-Url: https://codereview.chromium.org/2696193004
Cr-Commit-Position: refs/heads/master@{#452280}

[modify] https://crrev.com/e10fdac86b82f2e64a63815a9e08789582e6c8f9/components/data_use_measurement/core/data_use_measurement.cc