Record more download resumption UMAs to analyze the how download is resumed

Record more download resumption UMAs to analyze the how download is resumed

This CL adds the metrics to study how many resumption is attempted for a download.
This allows us to study the high download interruption counts.
And choose a better throttling strategy.

BUG=712318
TBR=dtrainor@chromium.org, isherman@chromium.org

Review-Url: https://codereview.chromium.org/2820193002
Cr-Commit-Position: refs/heads/master@{#465451}
(cherry picked from commit bbe9ad733bbdf501cc63db9b624cfed076d33c32)

Review-Url: https://codereview.chromium.org/2831603003 .
Cr-Commit-Position: refs/branch-heads/3071@{#51}
Cr-Branched-From: a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
Committed: https://chromium.googlesource.com/chromium/src/+/a74d0227cdfe9c570717e48439aafb73d42f3635

[qinmin, 2017-04-19 16:34:51]

Description was changed from

==========
Record more download resumption UMAs to analyze the how download is resumed

This CL adds the metrics to study how many resumption is attempted for a
download.
This allows us to study the high download interruption counts.
And choose a better throttling strategy.

BUG=712318
TBR=dtrainor@chromium.org, isherman@chromium.org

Review-Url: https://codereview.chromium.org/2820193002
Cr-Commit-Position: refs/heads/master@{#465451}
(cherry picked from commit bbe9ad733bbdf501cc63db9b624cfed076d33c32)
==========

to

==========
Record more download resumption UMAs to analyze the how download is resumed

This CL adds the metrics to study how many resumption is attempted for a
download.
This allows us to study the high download interruption counts.
And choose a better throttling strategy.

BUG=712318
TBR=dtrainor@chromium.org, isherman@chromium.org

Review-Url: https://codereview.chromium.org/2820193002
Cr-Commit-Position: refs/heads/master@{#465451}
(cherry picked from commit bbe9ad733bbdf501cc63db9b624cfed076d33c32)

Review-Url: https://codereview.chromium.org/2831603003 .
Cr-Commit-Position: refs/branch-heads/3071@{#51}
Cr-Branched-From:
a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
Committed:
https://chromium.googlesource.com/chromium/src/+/a74d0227cdfe9c570717e48439aa...
==========

[qinmin, 2017-04-19 16:34:52]

Committed patchset #1 (id:1) manually as
a74d0227cdfe9c570717e48439aafb73d42f3635 (presubmit successful).