The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/91ae3602104125b4afca4f76d2b2841fda80718f

commit 91ae3602104125b4afca4f76d2b2841fda80718f
Author: jkarlin <jkarlin@chromium.org>
Date: Wed May 25 14:05:38 2016

Record the number of freshness periods since a stale HttpCache entry was last used

This metrics records the number of freshness periods that have elapsed since a stale entry was last used. This will help us to determine the right time to prefresh resources (e.g., prefresh on cache hit if the entry's age is > 50% of freshness).

BUG=614355

Review-Url: https://codereview.chromium.org/2005753004
Cr-Commit-Position: refs/heads/master@{#395885}

[modify] https://crrev.com/91ae3602104125b4afca4f76d2b2841fda80718f/net/http/http_cache_transaction.cc
[modify] https://crrev.com/91ae3602104125b4afca4f76d2b2841fda80718f/net/http/http_cache_transaction.h
[modify] https://crrev.com/91ae3602104125b4afca4f76d2b2841fda80718f/net/http/mock_http_cache.cc
[modify] https://crrev.com/91ae3602104125b4afca4f76d2b2841fda80718f/tools/metrics/histograms/histograms.xml

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1b747469849d13851a4a5e9011a50548a0f45223

commit 1b747469849d13851a4a5e9011a50548a0f45223
Author: jkarlin <jkarlin@chromium.org>
Date: Wed May 25 18:52:11 2016

Record cache freshness metric per resource type

We're considering prefreshing resources by resource type, so it's
necessary to know how the breakdown of freshness periods since last
used by resource type.

BUG=614355

Review-Url: https://codereview.chromium.org/2009253002
Cr-Commit-Position: refs/heads/master@{#395947}

[modify] https://crrev.com/1b747469849d13851a4a5e9011a50548a0f45223/net/http/http_cache_transaction.cc
[modify] https://crrev.com/1b747469849d13851a4a5e9011a50548a0f45223/tools/metrics/histograms/histograms.xml

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/dc3cb4f7c2ca1f0ade7dcb560a8040ed2d13a695

commit dc3cb4f7c2ca1f0ade7dcb560a8040ed2d13a695
Author: jkarlin <jkarlin@chromium.org>
Date: Fri Jun 03 16:12:52 2016

[HttpCache] Record age of validated and updated stale cache entries

It would be good to know the correlation between an entry's age and its
likelihood to be validated vs updated. This CL adds two new metrics which
record the stale entry's age (as a percentage of freshness) when it's validated
and when it's updated.

BUG=614355

Review-Url: https://codereview.chromium.org/2036123003
Cr-Commit-Position: refs/heads/master@{#397720}

[modify] https://crrev.com/dc3cb4f7c2ca1f0ade7dcb560a8040ed2d13a695/net/http/http_cache_transaction.cc
[modify] https://crrev.com/dc3cb4f7c2ca1f0ade7dcb560a8040ed2d13a695/net/http/http_cache_transaction.h
[modify] https://crrev.com/dc3cb4f7c2ca1f0ade7dcb560a8040ed2d13a695/tools/metrics/histograms/histograms.xml