The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/afcc763ac1f0cec903036bfc1f61e05c8697bf01

commit afcc763ac1f0cec903036bfc1f61e05c8697bf01
Author: Min Qin <qinmin@chromium.org>
Date: Wed Aug 30 01:39:28 2017

Add new UMA to record the content length for parallelizable downloads

This is to study the size inconsistencies between parallel and parallelizable download.
Parallel download reports a larger file size than parallelizable download.
This UMA will allow us to tell whether there are more large download,
or parallel download is reporting wrong file sizes.

BUG=760327

Change-Id: I9f947dab6c60b83e0bebe142d44d30a774b99df1
Reviewed-on: https://chromium-review.googlesource.com/642354
Commit-Queue: Min Qin <qinmin@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#498335}
[modify] https://crrev.com/afcc763ac1f0cec903036bfc1f61e05c8697bf01/content/browser/download/download_item_impl.cc
[modify] https://crrev.com/afcc763ac1f0cec903036bfc1f61e05c8697bf01/content/browser/download/download_stats.cc
[modify] https://crrev.com/afcc763ac1f0cec903036bfc1f61e05c8697bf01/content/browser/download/download_stats.h
[modify] https://crrev.com/afcc763ac1f0cec903036bfc1f61e05c8697bf01/tools/metrics/histograms/histograms.xml