Adds metric to help assess last_n impact on tab restores. (M58 merge)

Adds metric to help assess last_n impact on tab restores.

This change adds a new metric to help us assess the impact of last_n on
the cases where an existing tab has to have its contents restored. This
change only affects Chrome on Android.

We track tab restores in Tab and call the appropriate, newly introduced
methods in OfflinePageUtils where the reporting actually happens.

BUG=688588
Review-Url: https://codereview.chromium.org/2754103003
Cr-Commit-Position: refs/heads/master@{#458530}
(cherry picked from commit e9f7809b63666b9c8c558dbde9397b4ce23fe119)

Review-Url: https://codereview.chromium.org/2767803002 .
Cr-Commit-Position: refs/branch-heads/3029@{#348}
Cr-Branched-From: 939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}
Committed: https://chromium.googlesource.com/chromium/src/+/79e7e4dafbc6b93344e3f71e872baafd80f7ca9e

[carlosk, 2017-03-21 23:05:39]

Description was changed from

==========
Adds metric to help assess last_n impact on tab restores.

This change adds a new metric to help us assess the impact of last_n on
the cases where an existing tab has to have its contents restored. This
change only affects Chrome on Android.

We track tab restores in Tab and call the appropriate, newly introduced
methods in OfflinePageUtils where the reporting actually happens.

BUG=688588

Review-Url: https://codereview.chromium.org/2754103003
Cr-Commit-Position: refs/heads/master@{#458530}
(cherry picked from commit e9f7809b63666b9c8c558dbde9397b4ce23fe119)
==========

to

==========
Adds metric to help assess last_n impact on tab restores.

This change adds a new metric to help us assess the impact of last_n on
the cases where an existing tab has to have its contents restored. This
change only affects Chrome on Android.

We track tab restores in Tab and call the appropriate, newly introduced
methods in OfflinePageUtils where the reporting actually happens.

BUG=688588

Review-Url: https://codereview.chromium.org/2754103003
Cr-Commit-Position: refs/heads/master@{#458530}
(cherry picked from commit e9f7809b63666b9c8c558dbde9397b4ce23fe119)
==========

[carlosk, 2017-03-21 23:07:13]

Description was changed from

==========
Adds metric to help assess last_n impact on tab restores.

This change adds a new metric to help us assess the impact of last_n on
the cases where an existing tab has to have its contents restored. This
change only affects Chrome on Android.

We track tab restores in Tab and call the appropriate, newly introduced
methods in OfflinePageUtils where the reporting actually happens.

BUG=688588

Review-Url: https://codereview.chromium.org/2754103003
Cr-Commit-Position: refs/heads/master@{#458530}
(cherry picked from commit e9f7809b63666b9c8c558dbde9397b4ce23fe119)
==========

to

==========
Adds metric to help assess last_n impact on tab restores.

This change adds a new metric to help us assess the impact of last_n on
the cases where an existing tab has to have its contents restored. This
change only affects Chrome on Android.

We track tab restores in Tab and call the appropriate, newly introduced
methods in OfflinePageUtils where the reporting actually happens.

BUG=688588

Review-Url: https://codereview.chromium.org/2754103003
Cr-Commit-Position: refs/heads/master@{#458530}
(cherry picked from commit e9f7809b63666b9c8c558dbde9397b4ce23fe119)

Review-Url: https://codereview.chromium.org/2767803002 .
Cr-Commit-Position: refs/branch-heads/3029@{#348}
Cr-Branched-From:
939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}
Committed:
https://chromium.googlesource.com/chromium/src/+/79e7e4dafbc6b93344e3f71e872b...
==========

[carlosk, 2017-03-21 23:07:15]

Committed patchset #1 (id:1) manually as
79e7e4dafbc6b93344e3f71e872baafd80f7ca9e.