The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5f9a48e44f1257972cb83947355c7298555ccc94

commit 5f9a48e44f1257972cb83947355c7298555ccc94
Author: twifkak <twifkak@chromium.org>
Date: Sat Feb 25 03:49:01 2017

Add Precache.Fetch.MinWeight UMA.

This collects the distribution of resource weights that are actually
reached before hitting the byte caps. This helps us tune the value of
PrecacheConfigurationSettings.min_weight.

BUG= 696035 

Review-Url: https://codereview.chromium.org/2711473006
Cr-Commit-Position: refs/heads/master@{#453059}

[modify] https://crrev.com/5f9a48e44f1257972cb83947355c7298555ccc94/components/precache/core/precache_fetcher.cc
[modify] https://crrev.com/5f9a48e44f1257972cb83947355c7298555ccc94/components/precache/core/precache_fetcher_unittest.cc
[modify] https://crrev.com/5f9a48e44f1257972cb83947355c7298555ccc94/components/precache/core/proto/precache.proto
[modify] https://crrev.com/5f9a48e44f1257972cb83947355c7298555ccc94/components/precache/core/proto/unfinished_work.proto
[modify] https://crrev.com/5f9a48e44f1257972cb83947355c7298555ccc94/tools/metrics/histograms/histograms.xml